Reply To: Lesson 8-2: Ratio and Rate Reasoning – Discussion

[Aaron Davis]

I don’t think I naturally think of ratios as multiplicative comparison, at least not for this problem. Maybe it is because I teach elementary grades, sometimes working with grade 5 but mainly with the younger learners.

So I naturally went the composed unit route, seeing the 2 ml of water per ml of rice or 1/2 ml of rice per ml of water. So I was scaling in tandem looking at the rice and water as one composed unit. Looking at it as multiplicative comparison though, just looking at the quantity of rice seemed very different and foreign to me, which I think is what you said, that thinking this way in the context of this problem is a huge stretch.

[Aaron Davis]

I don’t think I naturally think of ratios as multiplicative comparison, at least not for this problem. Maybe it is because I teach elementary grades, sometimes working with grade 5 but mainly with the younger learners.

So I naturally went the composed unit route, seeing the 2 ml of water per ml of rice or 1/2 ml of rice per ml of water. So I was scaling in tandem looking at the rice and water as one composed unit. Looking at it as multiplicative comparison though, just looking at the quantity of rice seemed very different and foreign to me, which I think is what you said, that thinking this way in the context of this problem is a huge stretch.