Compound Measures

I have been looking at compound measure with year 11 this week and we have approached it using ratio tables. I like using ratio tables and i think it can make students think more logically about compound measures instead of substituting into formulae.

For example; I asked the class the following question…

I walk 2 kilometres and it takes me 15 minutes. At what speed do i travel at in km/h?

I had several students trying to draw a triangle and write S, D and T in the sections then try and divide 2 by 15.

Some tried to divide 2 by 0.25.

One student said ‘if you walk 2km in 15mins, you’ll walk 8km in an hour’

2 –> 15mins

… –> 1hour

This made sense to the class and we went from there. There was definitely a sense that the question and the process made more sense like this.

Speed: Here are two slides of the same questions but one uses images the other doesn’t. Could be used as a match up or could be used to support students if they need it. Here’s the ppt: Compound Measures (Proportion)

speed 2 speed 1