# Category Archives: math

## Back to school, back to study groups

We started our first study group session on Friday with a quick review of multiplication. J- and V- warmed up by reciting the multiples of 6 to 9. Good retention from last year, and we’ll see how practice helps them improve. After the warm-up, we went over a shuffled deck of multiplication flashcards.

The teachers had given them a quiz in school, so we covered some of the topics they found confusing. W- and I explained the difference between convex and concave shapes using angles and lines. I drew different figures and quizzed them on the classifications. J- and V- drew their own figures, and they classified them together.

Squares and square roots were another point of confusion. We started off with a graphical review of what squaring means, and what a square root is. I used a tip from John Mighton’s “The Myth of Ability”: I tweaked my exercise to vary in scale without varying in difficulty. (What’s the square root of 31337 x 31337?) After J- and V- understood the relationship between squares and square roots, we covered approximation and factorization as ways of finding the square root. J- and V- practised finding the square root of numbers like 225 and 144.

We’ve encouraged them to take notes so that it’s easier to review lessons. The extra study group time will definitely help, too. Grade 8 will help students learn how to solve real-life problems, so we’ll be sure to show more of the calculations of everyday life. Here we go!

## The enemy of your enemy is your friend: mnemonics and negative integers

From April 26, Tuesday: J-‘s studying for Thursday’s “in-class performance assessment” on integers. (In-class performance assessment? What happened to the good old word “quiz?” Too much anxiety?) We’re spreading the review out over the next two evenings.

The test will cover adding and subtracting positive and negative numbers. J- and her study group are already off multiplying and dividing (which apparently don’t turn up until grade 8 – really?). W- made up a quick worksheet for J- to practise adding, subtracting, multiplying, and dividing integers.

“The enemy of your enemy is your friend,” I heard her say as she solved the exercises, writing down the correct signs for all the products and quotients. I grinned. I’d taught them that mnemonic two weeks ago. It’s a way to remember the results of multiplying or dividing numbers.

As I explained to the kids: you don’t have to stick to this in real life. Pou can certainly be friends with the friends of your enemy. But this might help you remember the signs for multiplication and division:

• The friend of your friend is your friend. Positive times positive is positive.
• The friend of your enemy is your enemy. Positive times negative is negative.
• The enemy of your friend is your enemy. Negative times positive is negative.
• The enemy of your enemy is your friend. Negative times negative is positive.
 A B Result Friend + Friend + Friend + Friend + Enemy – Enemy – Enemy – Friend + Enemy – Enemy – Enemy – Friend +

2011-04-26 Tue 20:05

Glad to see it stuck in her head! She answered all the exercises correctly (and quickly, too).

## Why we use more than math textbooks and general-purpose resources

For last Sunday’s study group, we focused on algebraic expressions. The kids were a little out of sorts at the beginning. “Math is boring,” one said.

“The way it’s taught in school, maybe. But math is really useful in life, so it’s good to learn it,” I said. I shared a few examples of saving money with math, enjoying life with math.

The group warmed up using a matching exercise, matching the word problems on the left side with the algebraic expressions on the right. Then we worked through some of the problems I’d prepared. In one afternoon, we talked about:

• cats and how much food they eat (1/4 cup, twice a day, 365 days, n cats…)
• T-shirts, sleeping cat toys, and chopsticks that look like lightsabers
• how much it might cost to eat onigiri for every meal, every day, for a year
• how long you might be able to eat onigiri given a particular budget
• Scott Pilgrim, Wallace, and Knives Chau
• more cats, including Neko on my head

There are several types of exercises. Completely abstract ones (here’s an equation, solve for n) get lots of confusion and little engagement. Practical exercises (how much would this cost after tax?) get some interest. Outlandish exercises drawing on the kids’ interests get lots of laughs – and solutions. So we mix practical exercises and outlandish ones, one to show math in real life and the other to get the kids involved. It’s like improv comedy, but for education.

This is where parents and tutors really need to step in and mix things up. Textbooks are written for everyone. They can’t take individual interests into account, and they can’t be revised each month to take advantage of pop culture references. When you make up your own exercises, though, you can do whatever you want.

I know J- likes Scott Pilgrim, Fruits Basket, and cats, so they turn up in math exercises. It’s not hard to pick up some standard forms of exercises from textbooks and translate them into more interesting situations.

Helping someone learn? Make up exercises based on their interests and see what happens.

## Hypercubes, happiness, and serenity

I remember reading an excerpt from Flatland in Childcraft when I was growing up, and wondering: how would a flat square understand this three-dimensional world we live in? In high school, I read a book about mathematical curiosities. Challenged by the idea of visualizing hypercubes and other higher-dimension objects, I turned to a trick I’d come across while reading: take what you see, use time as the fourth dimension, and imagine all the moments superimposed. Non-existence, birth, life, motion, death, and oblivion collapsed into a single space, further complicated by the rotation and revolution of the earth, the other motions of our galaxy and universe…

I had an existential moment: life is so short and insignificant!

And then I thought, “Hey, this is pretty cool.” I dipped into this imagined world occasionally, thinking about the past and future of places, objects, and people. It proved to be a useful test for relationships: what would life be like with the grief of losing this person – will it have been worth it? It also helped me let go of stuff. I could see myself before I got whatever it was, and I could see myself after.

You might say it’s an odd sort of happiness that maintains an awareness of death and insignificance, but it’s the sort of calm happiness that’s confident that everything will work out. Why get upset over something that will pass?

So when I came across the ideas of unconditional serenity and emptiness in Joseph Sestito’s Write for Your Lives (an approach that draws on Buddhism), I thought, “Hmm. That’s what they call it.”

It’s still a little strange to look at someone, stretch my imagination, and see them as child and senior, idea and memory. It’s good practice, though, and it reminds me that we’re all in the middle of our own journeys.