Ever the contrarian, Robert loves teaching fractions: he sees them as an opportunity to expand his students’ understanding of lots of mathematical topics, including ratios and proportions, probability, divisibility techniques and even geometry. Instead of seeing fractions as a crisis, consider it an opportunity!

Robert’s study of fractions also gives him a chance to clear up misconceptions that students might still have about how ratios and proportions work. One of the most prevalent misconceptions is that equivalent fractions can be created by adding or subtracting the same amount from the numerators and denominators. Thus we have students who believe that 3/8 can be turned into 4/9 by adding 1 to both numbers. Of course this is horse hockey, but because Robert is a constructivist (as opposing to being an instructivist), he prefers to create “compelling contexts” that would prove this wrong.

One method to impart the idea that proportional relationships are multiplicative (as opposed to additive) is to teach students by counter-examples. That is, use an example that shows that adding the same amount to the two parts of a ratio will not result in a proportion, and give students to the opportunity to prove the relationship false on their own.

Now some teachers may say, “but this is going to take a long time; wouldn’t it be easier if I just told them?” Yes, it would be “easier,” but you didn’t go into this profession because it was easy, you went into this profession because you want to teach! And by having your students figure it out on their own, you are actually teaching them to think. What’s the danger of that?

Robert likes to use visual models to help students understand this issue and you can do it very easily using a basic drawing program or a photocopy machine. In this case, Robert started with the 5th grade class photo and then put it onto the fancy copy machine with which he does battle on a regular basis. One of the features he has discovered is the panel that allows him to create an enlargement by setting the target size of the copy in inches independently, as opposed to percents proportionally.

Starting with the 5″ x 7″ photo, Robert changed the target sizes by adding 1″ to both the length and width of the photo: his new photos were 6″ x 8″, 7″ x 9″, 8″ x 10″, all the way up to 11″ x 13″ (the photocopier at his school goes up to tabloid size of 11″ x 13″; if yours doesn’t, then go to a copy show, where they can do it for you.) What do you think would happen if you enlarged a photo using this method?

Robert distributed the photos to the students in pairs of 2; they pulled out the rulers and measured the photos to the nearest inch (he makes sure they are done in increments of 1″) and then records them in an organized table of values so that students can see the enlargement pattern. They notice that the width of the photo is always 2″ more than the height, and that enlarging the photo by adding the same amount to the width and height resulted in distortion, particularly as the photo got larger and larger.

His students then “see” for themselves the importance of proportions when enlarging a photo: if you double one side of the photo, you’ve got to do the same to the other side to keep it looking right: if not, the result is a photo that looks “stretched out.”

Robert completes this lesson by reviewing how a ratio is set up and how two ratios can be evaluated to see if they create a proportion by using a “scale factor.” He then gives his students 16 different frames to match up while calculating the scale factor on each one.

Now here’s a question for you: if you’ve ever shopped for photo frames, how come they’re never proportional? A 4″ x 5″ print can’t be enlarged to a 5″ x 7″ print, but it can be made into an 8″ x 10″ print, but that can’t be enlarged to fit an 11″ x 17″ frame, which can’t be enlarged to a 13″ x 17″ frame. What’s the deal with any of this?

This is more than silly mathematics, by the way: our entire technical world is made more annoying by the fact that few of our devices use screens that are proportional to one another: the videos we shoot on our smartphones are not proportional to our tv screens, the widescreen movies we see in theaters are not proportional to our tablets or our televisions. The result is those annoying “letterboxes” that have to be inserted on the top and bottom of movies, or those pervasive and confusing messages that tell us that the original movie had to be modified (read: cropped or stretched) to fit our screens.

If you’re interested in using this activity in your classroom, check out this activity that I’ve uploaded just the other day:

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Since one of the hallmarks of our democracy is “one person, one vote,” it would be safe to assume that Party “A” also won 53% of the Assembly seats, while Party “B” controlled 45% of those seats. Or at least something close to that, right?

Well, no, as a matter of fact, the outcome of that election was that Party “B” ended up with 60 of the 99 Assembly seats, while Party “A” ended up with 39. To sum it up, Party “A” got 53% of the votes, but ended up with 39% of the seats, while Party “B” got 45% of the votes and took 60% of the Assembly seats, making it the majority party, and ruler of the legislature.

Does something smell a little fishy to you? I hope so.

This crazy mathematical outcome is brought to you through the magic of “gerrymandering,” where legislative lines are drawn so that one political party is favored over another. The mathematics of this is not terribly complicated: all it requires is creating districts where all the voters from one political party are either concentrated into a small area, or “diluted” into districts with voters from the opposing political party. This is a practice that has been around since the founding of the United States; it was even practiced by that great patriot Patrick Henry to prevent James Monroe from being elected to the House of Representatives.

This is a small example of what happened in our national election, where the candidate from Party “C” earned close to 3,000,000 more votes than the candidate from Party “X.” If this seems familiar, it’s because the exact same thing happened in 2000 election, when the losing candidate from Party “C” earned over 500,000 more votes than the candidate from Party “R.”

Part of the reason for this is that the concept of “one person, one vote” has always been a fictitious idea in U.S. history, sealed into our Constitution from the founding of the republic when slaves were counted as 3/5 of a free person for census purposes, yet deprived of the power to vote.

This meant that states with large slave populations were able to wield far more power than was mathematically possible if only free persons were counted. If you lived in a state like South Carolina, where nearly half the population was enslaved in 1790, then your vote was worth almost twice as much as other citizens (actually, a free white male with property) who lived in a state that had few to no slaves.

That principle is alive and well in our electoral college system, which gives disproportionate amounts of power to states with very small populations. A person living in state “W,” with a population of fewer than 600,000 people, has twice as much say in our national elections than a state like “NY” with over 3 times the population.

If all this is making you want to pack your bags and move to a “real” democracy, you’re not alone. However, through the power of mathematics, there may be a fix for places like Wisconsin (and many other states as well), where the voters choose one thing and end up with something very different. As this is being written, a major case is moving through the courts which will bring some fairness to the system, so that the majority of the voters will actually get the majority of power. Isn’t that a good thing to maintain a healthy democracy?

On November 21, 2016, a federal judge ordered the state of Wisconsin to re-draw the state districting maps based on a recently developed mathematical measurement called “the efficiency gap.” This is defined as “the difference between the parties’ respective wasted votes in an election, divided by the total number of votes cast.”

To put this into more understandable terms, the statisticians who developed this measurement came up with a number they called “wasted votes.” These votes come in two forms: the first are “lost votes” that are cast by people voting for the losing party, and “surplus votes” cast by the winning party. For example, lets say there is an election where five seats are up for grabs. The results for four of the districts is a 57% to 43% win for Party A, while the final district is won by Party B with an outcome of 85% to 15%. Party A gets 4 seats, Party B gets 1 seat. Sounds fair, right?

Not so fast, pal.

Had the districts been drawn differently, the 85% of the votes earned by Party B (a surplus of 34% over the 51% needed to win that district) could have been distributed over the other 4 races, giving Party B a better shot at occupying more seats. By doing a simple calculation, we find that there was an efficiency gap of 40% in Party A’s favor. If the efficiency gap was brought down to a more reasonable 3-4%, the actual outcome would give 2 seats to Party A and 3 seats to Party B, a much more “representative” outcome of the voters’ intentions. By re-drawing the districts so that there are fewer lopsided races like this, we actually end up with a more robust and representative democracy.

For those of you who despair at the state of our nation, it should be remembered that while it was mathematics that got us into this mess, it is ultimately mathematics that will help refine our government so that it is truly representative of the the will of the citizens.

This blatantly political post has been brought to you by SamizdatMath, where you can also find these fine materials that will cause you to think more carefully about our political and economic system:

And would someone please hit the “follow” star so that I can finally reach 500?

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But since you’re still reading this, you might as well stick around, because this actually is relevant for your teaching practice, and at worst, it would probably make you seem a lot smarter when talking to your supervisors, colleagues or the people you meet at parties who make snarky remarks about “only being a teacher.” If there’s one thing Robert loves is asking a hot shot attorney, “yeah, well, if you’re so smart, tell me, how would you teach invariance to a 5 year old?” and then watch as he takes a gulp of beer and 23 skidoos towards the corn chips.

Okay, here’s the 411 on “invariance” and why you’re going to see mathematics in a whole new light once you “get it.” Eventually, Robert is going to complete his master opus on this topic and then you can buy it at his store, but for now we’ll just dip our toes in the water and leave you with a few questions. But I’m not going to give you a “textbook definition,” because a) that’s boring, b) that’s not the best way to define a concept. Instead, I’ll give you a few examples, and you can work it out for yourself:

Now you all know that, because our man Piaget described that as one of the earliest forms of mathematical knowledge children exhibit, and which you’ve no doubt observed time and time again. Invariance shows up over and over again in mathematics education. Here’s another example:

Are you getting the idea? Basically, the concept of invariance shows up whenever we think to ourselves “it makes no difference if….” Robert loves to use this with his first grades when he hands out materials that comes in different colors.* “Okay, these geometric shapes come in red, blue and green, but the underlying function of these materials is invariant with respect to their color,” *he’ll say, followed by, *“can someone just translate what I just said?” *The first time he tried this out, a little girl raised her hand and said, “What that means is that you get what you get and you don’t get upset.”

Less we think that this is just something that shows up in the early childhood years, let’s look at an example from the upper elementary grades:

The above insight came to Robert while observing a student work on one of these cruddy worksheets that a teacher had unfortunately downloaded from the interweb. He asked the student whether it was necessary to re-calculate the area of several triangles which had identical bases and heights, to which she shrugged her shoulders and replied, “I guess so; they’re all different shapes….”

Want to see where this is going in the upper grades? Sure thing: according to Robert, show him a student who is having trouble with solving algebraic equations, and he’ll show you a student who is struggling with the concept of invariance:

If you’ve been following Robert for any amount of time, you’ll know that helping teachers find a “theme” that carries over from year to year is an important aspect of his work (as well as giving young children brain-busting unsolvable problems….) But if you understand even a little bit about these underlying themes, it will make you a better teacher.

**Your Assignment: **What mathematics topic are you teaching right now to your students? Do you see the concept of invariance showing up in that topic? How would it help your students better understand the mathematics that they’re learning?

*This post has been brought to you by SamizdatMath. Yes, we want to sell you stuff, but our stuff doesn’t keep your students’ busy or look cutesy. Our stuff actually makes your kids “think!”*

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While taking a morning walk along the streets of his Free State of Brooklyn last week, Robert happened upon a brand new sealed and complete set of teaching guides for something called “Math 180”, which the publisher’s website describes as follows:

MATH 180 is designed to address the needs of struggling students in grades 5 and up, and their teachers, equally—building students’ confidence with mathematics and accelerating their progress to algebra.

I’m going to assume the part about addressing the needs of students AND teachers is an attempt to acknowledge the fact that many teachers of mathematics are unprepared to actually to do their jobs. Mathematics is a technical subject, and unfortunately, many of the teachers who are in the position to educate students in this area are inadequately trained or supported. This is not because they are inept or uncommitted, but because of the low standards of preparation and understanding that we are willing to accept in our schools.

So Robert schleps home with this box of teaching manuals, which consists of 6 different thick books, a very retro looking CD (remember those?) AND a thick packet of classroom posters, all of which weighs in at just under a fully loaded Mini Cooper. Opening to the “Math 180 Experts” page, Robert finds the usual gallery of “Lead Authors”, “Advisors,” “Contributors,” and the members of an “Educator Advisory Board,” each of whom was most likely offered a nice chunk of change to act as if any of them had any hand in the creation or production of this scheisse.

Robert was impressed at how the people who actually put together this curriculum worked to check off every kind of educational trend, scattering in references to Carol Dweck’s “growth mindset,” to “Universal Design for Learning,” along with “blended learning,” “formative assessment,” and a host of other educational hot topics that probably stimulate the endocrine glands of people who love this kind of stuff. Don’t get him wrong, Robert adores Carol Dweck, and believes that UDL is good stuff, but if you delve a little deeply, you would see that the actual curriculum violates all the precepts that the aforementioned experts would advocate. Oh, and just to make things they didn’t miss ANYONE, they also listed two “advisors,” as well as one “contributor” from Singapore, because we all know that including that semi-repressive city-state’s name in the context of mathematics education will be just the poke textbook adoption committees need in order to sink massive amounts of public money into this cruddy program.

Once you get past all the marketing materials, you see a pretty dull curriculum which uses all the standard models to remediate middle school students who have either fallen behind or were “turned off” by the mathematics instruction they had before. I was especially impressed by the “relevant” word problems the copy editors included. Check out a few of the following:

Well, we think you get the point: same old “pseudo-content,” same old teacher centered instructivist methodology, same old reward based assessment (you get “badges” if you reach certain levels while using the online learning materials), all gussied up and pre-digested for your use. Okay, we understand that Scholastic, and the marketing agent, Houghton-Mifflin Harcourt YouNameIt, are profit-making concerns and need to return “value” to their shareholders (which probably includes companies like TIAA-CREF, which manages retirement plans for educators), but c’mon, really? You have all these talented authors, advisors, reviewers, copy editors and art directors, and this is the best you can do?

Robert would especially like to castigate the cast of characters who were bought off to put their names and photos in this worthless pile of junk. Okay, we know the teaching profession is not especially well-compensated, but Deborah Ball, you’re a dean at the University of Michigan! We’re sure you get excellent health insurance and retirement benefits, so is it really worth selling your good name to be a pretend “lead author” of something you probably spent a few hours red-penning over your morning coffee? Let’s get real: Scholastic really should have used its budget to create interesting and compelling content, instead of squandering it on empty endorsements, outdated methodologies, fancy graphic design and inept copy editing.

*This post was brought to you by the entirely unprofitable concern known as SamizdatMath, and matho-educational syndicate which develops and self-publishes uncompromising mathematics materials for teachers in grades pre-K and above. This particular rant was brought to you by:*

Readers, do you live in fear of teaching division to your students? Do you stay awake at night laboring over unique division examples that come out evenly? Do you squirm every time a student looks up and says, “but blach doesn’t go into blah-blah-blah?” Do you drift off into la-la-land whenever a student complains, “hey, there’s a remainder here; what should I do with it?”

If this bothers you, then consider the options of using the duodecimal system, aka “base 12.” In the base 12 number system, you have many more options to give division problems that are “remainder free!” Yes, now you can strike one less issue off your list: fewer remainders means neater division problems, no complaints about extra numbers and, most importantly, fewer decision to make! With the duodecimal system, you can divide by 1, 2, 3, 4, 6, and 12 without worrying about pesky remainders! Try that with the crummy old decimal system: divide by 3, 4, 6, 7, 8, and 9 and what do you end up with? REMAINDERS! Urgh!

Okay, the world will not be switching away from the base 10 system anytime soon, and remainders are going to be a fact of life well into our collective future. So the question is this: what should you tell your students to do with the remainders that inevitably come from dividing?

a) Do the problem over; all division problems in school come out evenly.

b) Write it as a whole number, and let someone else deal with it.

c) Leave it as a fraction, whatever that is.

d) Leave it as a decimal, so long as it comes out evenly. If not, refer to choice “a.”

e) Round up to the nearest whole number.

f) Round down to the nearest whole number.

g) All of the above.

h) None of the above.

i) Check Khan Academy.

j) It really depends; remainders on division problems are highly contextual.

Well, if you know my style of writing, you know the answer is “j,” but given how many teachers treat math as a set of “rules” to be obeyed, it is most likely that a student will choose a, b, c, d, e and/or f. Harumph….

The simple fact is this: most division problems do not come out evenly, and why we persist in giving students a steady diet of problems that leave no remainders is beyond my comprehension. The presence of remainders should not be seen as an “oddity” when dividing; rather, we should teach it as one of the essential properties of how division works: most numbers do not go into other numbers evenly, or even once (the “bigger into smaller” issue, which I’ll cover in another rant…), and yet we persist in giving students a steady diet of division situations which work out evenly. Therefore, if we give word problems where remainders are the exception, rather than the rule, our students are not going to have strategies for dealing with remainders.

Consider the five problems shown below, all of which have remainders, all of which require different interpretations.

In the first problem, the remainder gets discarded, while in the second problem, the remainder should be written as a decimal. The third problem is best left as a fraction, the fourth problem needs to be rounded up and the fourth problem doesn’t even need division at all: just multiply 7 boxes times 6 donuts per box and you end up with 42, which is larger than 39. Do I have to do everything for you?

Teachers of mathematics, we have to wise up! Give your students lots of word problems where the divisor doesn’t gozinta the dividend evenly, and have them interpret the meaning of the remainder. It’s either that, or push for decimal reform and invest in base 12 calculators!

This post has been brought to you by the hardest division assessment you could ever give to a student who believes “I know everything there is to know about division.”

Hand your students a calculator and watch their brains sizzle! Comes complete with teaching tips, answer key and suggestions for activities that you can do in the classroom.

]]>As I struggled through the first year, the head of school, with whom I found myself at odds with, offered me a book called “The Art of Teaching” by Gilbert Highet, which actually proved to be my undoing when I attempted to implement the ideas expressed. I had actually read another book about teaching when I was 14 years old, 36 Children by the wonderful Herbert Kohl, which got me thinking about teaching as a force for social justice. My first year was rough, but it was then during that year that I understood, I was born to teach. I also learned that the idea of “teach, test, teach” just was not the essence of the profession. There was much, much more to learn and do….

Flash forward 32 years, and here I am, back where I started: a new year, new thoughts about teaching, and new things to do. I stopped in to visit the lovely teachers who rule the 2nd grade (or, what we call the “7/8s”) and what did I find but a lovely activity based on Eric Carle’s beautiful story, Rooster’s Off To See The World. As with all of Carle’s books, the illustrations are engaging, and the story works on many levels – it is nominally about a group of animals out for adventure, who ultimately opt for the “creature comforts” of home. At the same time, it is a counting book, designed to introduce the young to numbers and patterns. The teachers had posed a problem to the students: if there are 14 animals off to see the world, how many legs would they have? This is not an easy question, because some have 2 legs while others have 4, and there are 14 numbers to keep track off, which is no easy task for a child (or even an adult.)

I looked at the book very carefully and decided for myself, well, this is a wonderful book and the idea of keeping track of legs on animals is a provocative one for young children to do. But I also thought that turning the tables on the activity, that is, giving young children the chance to ask questions of one another, would be a fun and engaging way to get them to interact with one another.

There was just one problem with this plan: there is a great deal of variety in the legibility and spelling of 2nd grade children, as well as their motor skills in writing out questions. I wanted them to create problems quickly, so that they could focus on the mathematics, rather than letter formation, sentence structure, grammar and punctuation, to name a few elements of literacy. I also didn’t want to get into trouble with the publishers of Mr. Carle’s book due to copyright infringement, which meant staying away from his imagery and characters.

Instead of rooster, cat, frogs and turtles, I decided to simplify the activity by using only 3 animals. At the same time, I wanted to vary the number of legs on the animals, that way I could have more combinations: so I used an ostrich (2 legs), wombat (4 legs) and ants (6 legs.) I also think that ostriches, wombats and ants are interesting animals, don’t you?

With those decisions made, I designed three different stamps that students would cut out to make their questions: instead of writing out long sentences with stories, I envisioned them cutting and pasting combinations of the animals, with the simple question “How many legs?” printed underneath.

Well, this seemed like a promising start, but why stop at just addition? Since subtraction is also a good topic, why not create a simple problem that involves comparing the number of legs?

and while we’re at it, why not add something even more interesting and open ended?

Oh, this is muy muy fun, and if you don’t agree, well, you just don’t know what the definition of fun happens to be….

To add finishing touches to this activity, I thought about what could be done to get kids to think more carefully about how they create their problem, as well as offering a means to initiate discussion of their solutions. Which is why I created a separate sheet where they could make an answer key for the question they asked, as well as offer a “clue” about how to approach solving the problem:

Isn’t this beautiful? Well, that’s not all, because I added one more innovation which I think I may use on every single activity I make in the future:

Do you get what I’m attempting to do here? Instead of putting the name of the students at the top of the paper, which is what you do when you start something very monotonous (like take a test or apply for a learner’s permit at the DMV), I thought it would be much more important that a student “sign off” on their work *after* *it has been created. *Much like no artist every signs a work before creating a sculpture, painting or dance piece, a student should not sign off on a piece of mathematical thinking until after it has been completed. This allows the student to feel a sense of process and completion to what they have done. I feel very inspired by this tiny little change, and I hope you’ll use it as well.

The scariest thing I can imagine about being in my profession is doing the same thing year after year. Working with a staff of vibrant educators means that I always have the opportunity to do more and more, as well as refine what I’ve already done, AND share it with the rest of you. At 32 years in, I’m still feeling young…

*This post has been brought to you by…..*

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Carol Dweck, author of “Mindset: How You Can Fulfill Your Potential,” has long been one of Robert’s favorites in the field of educational psychology (his shortlist of the overrated and the “just plain terrible” includes Jo Boaler, Dan Meyer and Angela Duckworth, who all started out with such promise….)

So when he spotted this article posted on the The Facebook, Robert was reminded of the necessity of talking to children about how they should view themselves in learners. Now, Robert works with kids as young as 4, all the way up to 14, so in this decade long span, there are lots of ways to communicate how one gains proficiency in mathematics, but it must be consistent and constant.

Here’s his story:

*“I was working with a fourth grade class one morning, when a young man sat down next to me to work on a set of geometric puzzles I had created. As he worked, the child got more and more frustrated, and eventually muttered aloud, “man, I really suck at this.” I looked over at what he was doing and said, “yeah, a lot of kids find this tricky at first. It usually takes them a long time to finish the first few, but then once they get familiar with the pieces, it gets easier.”*

*Of course, the kid fell asleep during my soliloquy, so much of what I said was ignored. He went back to work, and after a few minutes once again stated, “I really suck at this.”*

*Remembering my grad school professor’s admonition that I talk like kids talk, I turned to him and asked, “Mergatroid, how long have you been working on this puzzle, anyway.”*

*“Oh, it must be like an hour…”*

*(It was actually more like 5 minutes; maybe he needs to try out this activity to sharpen his skills at time perception.)*

*I corrected his time assessment, and said the following:*

*“You know, you can’t know if you suck at this yet; it’s only been 5 minutes….”*

*“Well, how long will it take me to know?” he replied.*

*I thought about his question very carefully. On the one hand, I wanted to be realistic that some things in mathematics take time to understand and master, yet I wanted to encourage him to persevere to completion of the task.”*

*And with that, I said this:*

*“Oh, I would say about 20 years….”*

*“20 years?”*

*“Yeah, I’d say 20 years would be a fair amount of time to spend on something before you could say you sucked at it. You really don’t suck at these puzzles yet.”*

*“So you’re saying I should spend 20 years working on this puzzle?”*

*“If that’s what it takes; but my guess is that it won’t take anywhere near that long…”*

*And with a shake of his head, my friend went back to working on the puzzle, which he later solved in the afternoon.*

This (thankfully brief) story summarizes a lot of what Carol Dweck has been trying to advocate in her work, albeit with a twist. According to Dweck (who is not the first person to advocate for the “growth mindset,” by the way), the most important word to use when describing the challenges facing a child is the word “yet.” When we use this common and simple word, we are expressing our confidence that a child will persevere when facing a challenge which appears to be overwhelming.

The pivotal moment in Robert’s understanding of this word was when he was evaluating a young man whom he observed banging his head during a class he was visiting in North Carolina. When he sat alone with the child later in the day, he asked why he felt so challenged by math.

“Teacher says I don’t know my multiplication tables,” he explained.

“Oh,” I replied, “well, that’s a very common problem, even for adults. Tell me, what is 5 x 4?”

The young man responded, “5 x 4 is 20.”

“Oh, so you do know that one. How about 6 x 6?”

“6 x 6 is 36.”

“Good; how about 9 x 5?”

“9 x 5 is 45…”

This went on for about ten minutes; what it turned out was that this boy knew almost all of his multiplication facts, with the exception of the “difficult” ones (8 x 6, 7 x 8, 6 x 7, etc.) Every time he came upon one of these facts, he was reminded of what his teacher said and got angry at himself.

“You know, Will, the problem is not that you don’t know the multiplication facts. There are only about 4 or 5 out of the hundred facts that you are still stuck on. **You don’t know all the multiplication facts yet.**

With that, Robert could see his man’s face change a bit. He continued:

“Knowing 95 out of 100 facts means you know 95% of of the multiplication facts; in my book, that’s pretty good. Sure, you should learn the other 5%, but that wouldn’t be that hard, would it?”

And with that, young Will actually started to smile.

This little word has been Robert’s favorite word to describe the challenge of learning mathematics, whether it is a 4 year old struggling to count to ten or a 14 year old attempting to factor a quadratic equation.

“You can’t be bad at this yet. Give it 20 years, and if you haven’t seen yourself improve, well, then you can say you’re no good at it, okay?”

“But Robert, 20 years is a long time!”

“Well, you don’t want to give up too soon….”

This post was brought to you by the following resources Robert publishes and even makes a few pesos from now and then:

]]>One of the things that really irks Robert are math activities that focus too much attention on peripheral activities, like coloring, cutting and pasting. These projects look very pretty when completed, but unless the teacher’s specific goal is to create a work of art, they are pretty much a waste of time.

At the same time, it could be useful to take a break from using pencils and screens to do math, and cutting and pasting are good for motor skill development, so why not let the kids have a change of pace? How can we design a cut ‘n paste activity that makes the most of a student’s limited time in math class, without unduly devoting the majority of time on scissors and glue? How can we maximize the amount of thinking that will take place?

One thing that has to be considered is on designing the “cut outs” so that it can be cut out efficiently and with a minimum of wasted paper (which is why Robert objects to the use of most “cutesy” clip art that routinely gets inserted into many materials.) Check out the “cut outs” used in a 3rd grade activity below:

There are three reasons to object to this: the first is that it is difficult for young children to cut out, what with the individual pieces and rounded corners. The second is that there is a lot of white space between the different “cut outs,” which mean that it is a waste of paper. Third, since there are more symbols than actual problems, the students will be cutting out materials that are unnecessary. While the activity may be useful, this is seriously bad design. After making all the cuts (there are 13 separate pieces, at 4 cuts per piece, which is 52 different cuts, not to mention the time rounding out the corners) how much time do you think will be left to “do math?”

Robert approached the “cut ‘n paste” activity and redefined it as a design challenge, seeking to have the most “work” with a minimum of cutting. Here’s what he came up with:

What you’ll notice is that there are no rounded corners to trim, and that almost every piece is adjacent to another, so that one cut actually trims 2 separate pieces. The 24 pieces can be separated from the main sheet with two easy straight cuts, and then laid on top of one another two at a time to minimize cutting. The fifth graders who did this activity typically were ready to place their pieces in fewer than a dozen “cuts,” which look about 3 – 5 minutes. In addition, there was a minimum of paper waste, as the activity only left behind two small squares of paper and 2 thin strips.

Since Robert is a calculating guy, he figured out that there was less than 5% wasted paper, and 90% less cutting than other activities of this type. With less time on cutting, the students had much more time to think about much more important things, like “if 1/7 is .142857 on the calculator, and it’s rounded off to .142, why isn’t there one on the sheet?”

This post has been brought to you by…..

]]>Where does one begin to explain all the problems with this?

The beginning part of this is not all bad: true, multiplying by 2 is also the same as doubling, and yes, you could double a double to multiply by 4. But really, do you think there are a lot of 8 and 9 year olds who can *double a double a double? * You can almost see the smoke coming out of little Hudson’s ears as he attempts to double 8 three consecutive times: 8 + 8 = 16, 16 + 16 = 32, 32 + 32…. wait, where was I?

Things only get worse as you get further down the chart: yes, multiplying by 0 always equals 0, but does a child really need to memorize this fact? If the student understands the meaning of multiplication, then reciting “times zero = zero, zilch, nada….” and “times 1 = the other factor” is just nonsense. These are essential features of our number system that require understanding, not memorization: times 0 is the “zero property of multiplication,” and times 1 is the “multiplicative identity.” Yes, the word “multiplicative” is a mouthful for a young child, but this chart totally ignores the totally interesting properties of 0 and 1.

But the real howlers are multiplying by 10 and 100. The “adding zeroes” shortcut is incredibly wrong and will only lead to misconceptions the following year when the student learns about multiplying decimals, when he will end up writing down the following:

Make no mistake, this error will not go away in 5th, 6th or 7th grade. In fact, the idea that you multiply by powers of 10 (whether that be 10 or 100 or 1,000 or 10,000 and onward….) by “adding zeroes” is a hard one to shake at any age.

Robert says this: STOP TEACHING ADDING ZEROES AS MULTIPLYING BY POWERS OF TEN!

What should we do instead? Show students that multiplying by 10, because we are in a base ten system, “pushes” all the digits over one place to the left, and that zeroes “rush in” to fill those places that are left empty….

The beauty of teaching multiplication by powers of ten this way is that **it will always work!** It will work with whole numbers, negative numbers, decimals, irrationals, rationals, you name it, it will work!

This post has been brought to you by this guide to teaching place value, from which it has been excerpted:

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Such was the case when a reporter covered Andrew Hacker and his very convincing case for eliminating the traditional “advanced math” curriculum. We all know this as the algebra-geometry-trigonometry-advanced algebra, yadda, yadda, yadda forced march that college and capital accumulation bound high schoolers must march through. This sequence allegedly prepares the few students who actually understand this stuff for brilliant careers in art history, restaurant management and human resource development. It’s not that Hacker dislikes mathematics or wants to dumb it down; rather, he suggests that maybe a more thoughtful approach focusing on “real life” uses of mathematics would actually achieve the goals we have set out: prepare our students to participate in our quasi-capitalistic economic life and pseudo-democratic political system.

While we’re at it, Robert wishes Hacker would also take a more courageous stand, and push back against the teaching of fractions in the elementary grades. Talk about a waste of time: while fractions were a useful thing to know if you were a working class Sumerian over 5 millennia ago, today they’re just that like that unwelcome uncle who pops up at the Thanksgiving dinner table each year: nobody knows why he’s there, and everybody would digest much easier if he just stayed in his cardboard box.

As Robert tells it, fractions had a good run, and with a 5,000+ year history, they’ve outlived every fad imaginable, including paisley togas and virgin sacrifices. Fractions began their long run with the Egyptians, who utilized them to divide up plots of land and levy taxes. The ancient Sumerians loved fractions so much that they invented the 24 hour day, the 60 minute hour and the 360 degree circle just so they could divide them up into equal pieces really easily: a 24 hour day can be divided into halves, thirds, quarters, sixths, 8ths, 12ths and 24ths (don’t get me started on how easy it is to divide 60 and 360….) You just can’t do that with 10 or 100.

But Robert maintains, fractions are pretty much dead so far as common usage goes, and you can blame that on the French. Yes, those Jerry Lewis and croissant beurre loving eggheads are to blame for the downfall of fractions and the rise of its bitter opponent, the easy and convenient (and mostly sanitary) decimal notation. *Quelle barbe! *

Whatever your feelings for the French, which can be determined by what you call fried potatoes served with ketchup, you’ll have to admit they were on to something by inventing and then adopting the metric system: it’s soooo easy to use! No one who has ever worked with kilograms, meters or liters (as well as newtons, joules and candela) has ever had to struggle finding a common denominator, convert to a mixed number or inverting and multiplying. Is it any wonder that 99.9% of all the countries in the world use decimal units of measurement?

But here in the United States, we love our fractions, which means that it is the only place on earth (well, toss in Liberia and Myanmar) where fractions have to be taken seriously. Open a cookbook and what do you find? Fractions of a pound, fractions of a cup, fractions, fractions, fractions! Robert believes cooking is a pretty pleasurable experience, up there with consensual sex, open-water swimming and playing the concertina, but when you mix in fractions, well, you’re just asking for trouble. Robert wagers that there is a significant fraction of the American population which hates to cook because they’re scared of fumbling with quarter cups and half-pounds.

Open a cookbook anywhere else in the world, and there will be nary a fraction in sight: everything will be measured in grams, kilograms and liters, which makes life quite a bit easier. Don’t need an entire kilogram? Just put a decimal point on it, baby! Need to increase a recipe by ten times? Push those digits one place to the left and move on! You just can’t do any of that with half-tablespoons of vanilla…..

And this just has to do with cooking; the prevalence of fractions in American life, from our use of 8 1/2 x 11″ sheets of paper for correspondences to road signs which tell us our exit is 3/4 of a mile away is just so passé. I agree: I know decimals will take some getting used to when it comes to our everyday life, but can’t we give it chance?

Truthfully, Robert loves teaching fractions, and even makes a pretty good living off of them, seeing as how 4 of the top 5 bestsellers at his online store are about… fractions! Even I think they have some important uses, especially when it comes to algebraic notation, and they can be rather fun when done in a playful and non-threatening way.

However, in an era of high-stakes testing and curriculum standardization, maybe it’s time we reconsider the teaching of fractions in elementary school. Fractions prevent our students from solidifying more important concepts and mastering developing skills. They are confusing and have limited uses, yet we persist in teaching them to children who are just not equipped to understand them. Can we agree to delay them until 5th, 6th or 7th grade, when kids are more able to comprehend them, and can be covered in 1/4 the time?

I would wager that 93/95 of the American population would agree with me.

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