MPM1D1 - Day 36 Surface Area, Exponents & Compound Interest

We did the extensions to the Big Nickel today (interior angles, exterior angles, cost to resurface, etc.). This provided some great review on topics already covered to date. It was interesting to watch them struggle with surface area. Right away they jumped to their formula sheets and started looking at formulas for triangular prisms. The trouble was that many of them couldn't make sense of the variables on the page. Now to be fair we haven't done any work with surface area. I stopped the class and asked what surface area means. They knew exactly what it was. I asked them to show me which parts of the nickel we had to find the area of. They nailed it, so I set them to work to find the area of all the pieces. No formula required. I can't believe I thought we'd get the entire task done in a day.

Once we finished with the nickel it was time to head into exponents. I threw this question up on the board and asked them to come up with an answer individually.

It was great to see where everyone was starting from. One student said "This is easy! I just have to multiply 3 by 3 by 3..." and off he went. Others used the exponent button but got caught up on  the order of operations. Many students found the value of the numerator, then found the value of the denominator, wrote both of them down then did the division. A handful of students were able to use the exponent laws to quickly realize that the entire expression was equal to 1. After getting all of the errors corrected a student who knew the rules wanted to share, so she told us how to do it.  It was such any easy transition into what is often a boring list of rules.

As we discussed the rules one boy asked why we needed exponents. He understood that the rules were helpful in evaluating the expression above but wondered when in his life would he ever come across exponents. This sidetracked me as we discussed one of my favourite mathematical topics: compound interest.

I'm always surprised that students aren't aware that they are paid interest by their banks. In any case we talked about compound interest and how if you set aside money every month for the majority of your live you can become quite wealthy. When I was in high school my classes received these types of lessons from Bob Gunter. I had Bob as a teacher for four out of seven math courses. To me these lessons were the most memorable parts of any course. It was clearly something he was passionate about and he was able to share and spread that passion to his students. So Monday (tomorrow is a professional activity day) we'll look at some financial scenarios (at least a little bit).

I handed out some exponents practice and bid the class a happy and productive weekend.