(Math) Things I learned and Still Remember from Elementary School

There are a number of things I remember learning or figuring out in primary school that piqued my interest in Mathematics. These memories have stuck with me over the years and have left me with a continued sense of curiosity about the subject. I don't doubt my current desire for learning higher maths was seeded quite early in life. Most of it came before grade 6 and from a single teacher, Mr. Henderson.

12 Times Table

My first detention that I can recall. The principal of the school, Mr. Henderson, took me aside for doing something I shouldn't have been doing. Though I can't recall what I had done that particular day, I did tend to get in trouble a lot back then, I do remember the punishment. He gave me an index card and told me to fill it with the times table from 1x1 up to 12x12. This was in grade 2 or 3 and at that point we had only covered multiplication of smaller numbers.

I do remember sitting there writing out the columns of numbers. When I progressed up to uncharted territory, 10x12=120, then 12 more is 132, 11x12, and finally 12 more is 144, hence 12x12! My first moment of math eureka and I still remember quite vividly. The gratification of working these out on my own was quite a productive detention.

mm,cm,dm,m,Dm,hm,km

Say it 3 times fast: millimetre, centimetre, decimetre, metre, decametre, hectometre, kilometre. It feels like we said it a million times back then. But when thinking back to primary school I remember doing this quite vividly. Coincidentally the same principal was my drill sargeant for the metric prefix memorization.

Exponential Growth: 1 penny, 2, 4, 8, ... vs $100 + $100 + $100 + ...

exponential

Mr. Henderson posed the question something like this:

You have a job that for each day of work you choose either to be paid 1 penny on the first day, 2 on the 2nd, and each day the pay doubles; or, you take $100 from day one and get that same pay from then on. Let's say you have this job for a month. Which pay should you choose?"

The class was evenly split on which to choose. When we worked it out the class was floored. How a penny doubled into millions so quickly before the end of the month was a surprise to most of us. Though I had the intuition to pick the doubling side, two to the power of Thirty (2^30), even in pennies, is much bigger than I could have intuitively guessed. I did have a reasonable sense of regular growth by that point which I will get to next.</p>

Interest on a Million Dollars

A classmate recently recalled that this was in grade 3 but I think it came a little later, mostly likely grade 4 or 5. The question was, "What would you do if you won a million dollars in the lottery?"

The teacher went through the class asking each student about what they would do with the money. Most talked about what they would buy with the money. When it came to my turn, I remembered when I had opened a savings account at the bank recently and I did my best to learn about interest and compound interest. So I explained to the class that each month the bank would give you interest money on the million dollars--and then interest on your interest. Instead of spending the million dollars I would put it in the bank and spend the interest they gave me every month and not touch the principal amount. Though interest was a lot higher in the 1980s.

Another bit of wisdom from elementary school principal that has stuck with me over the years:

In anything you do, there are people better than you, just as good as you, and not as good as you.

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