# Day 92 – Intro to Related Rates

I deliberately teach topics in a different order in my AP class and in my non AP class because it gives me a chance to reflect and give it a try later in the year. We did related rates in November or something for AP, and we are doing it now in non AP. Sam posted his materials for Related Rates, and this really help me reorganize my unit. We started off today just by drawing what a circle with a constantly increasing radius would like, and what a circle with a constantly increasing area would like. I think this was a nice intro because I noticed that whenever my students draw diagrams for Related Rates problems, they make them somehow reflect that the object is changing, which is something I've never really seen them do before.

### 3 responses to “Day 92 – Intro to Related Rates”

1. suevanhattum

Have you ever seen a related rates problem that doesn’t use time as the variable?

I’m thinking about how I’ll teach it, and wondering if it would be right to say that we’re always thinking about rate of change of one thing with respect to time, compared to rate of change of something else with respect to time.

• I thought about this, and no I don’t think I have! Maybe something with marginal profit and marginal cost?

• suevanhattum

I told them it was “almost always” with respect to time. (I don’t care for those cost and profit problems, so I won’t go searching for them.) I think some of the books I’ve looked at have even defined related rates as being with respect to time. We did a few last week, and we’ll do a few more after Spring break.