Related rates, part 2: A few more tips

Three more examples of related rates problems. We emphasize the question of when you should and when you should not substitute the value of a variable quantity into the variable, and we look at the possibility of using two or more relationships simultaneously.

[微分積分入門]

12:05 The unit of measurement may be in/min.

[JossinJax]

I'm baffled by the lack of views here; these vids are stellar.