## Tuesday, October 19, 2010

### Potential Slope Memory Tool

Let me start by saying that I am not in the least bit a religious person. I do watch movies and TV and live in the world, so I think I know how certain religious people do the "sign of the cross".

Today I was trying to get some geometry kids I was tutoring to remember how to calculate slope when given 2 points. In various states of nonknowing, they either didn't remember at all, or they only knew how to do it on a graph, or they kept messing up and calculating, m = (x2-x1)/(y2-y1).

We got out the graph paper, and they remembered "rise over run". So I (again) linked that to "what changes when you rise?", "when you run?". And I tried to link that to m = (y2-y1)/(x2-x1). Anyway, as I was gesturing with my hands: rise (and my hands were moving up and down and up and down) over run (and my hands were moving side to side etc), I reminded myself of making "the sign of the cross". I double checked with the kids, and yes, the up down motion comes before the left right motion, so I said, "well if you want to remember which is which, then think of making this sign, and and the up/down is first, so that's (y2-y1) change, .....".

Then a kid joked that you also want to say your prayers before you do math (or take the math test).

In other weird/new-to-me tidbits. For various reasons, today I briefly mentioned congruent in geometry, and said that soon we'll think of shapes as being congruent when they .... . And the kids said, "same shape and same size." Then one kid raised her hand (and others confirmed) and wondered out loud why when she learned "congruent" in elementary school, she learned "same shape, same size, and same color". ????? I've never heard of this. Have you? Why stop there .... same: smell, texture, .... There must be something else that was going on that I'm not aware of.

#### 1 comment:

1. Charlotte10:43 AM

I'll try your sign of the cross suggestion. Even my Precal students sometimes get confused. That might help!
Maybe the kid who asked about color learned to play the game Set.