Question

Stan drove for h hours at a constant rate of r miles per hour. How many miles did he cover during the final 20 minutes of his drive?

Answer 1

20 minutes is $\frac{1}{3}$ of an hour (60 minutes).

Stan's constant rate is r miles per hour, which means he drove r miles in 60 minutes. So how many miles did he drive in 20 minutes? As explained in the first line, 20 minutes is $\frac{1}{3}$ of an hour. Since his rate is constant, Stan would drive $\frac{1}{3}$ of what he cover in 60 minutes, which is r miles.

Hence, Stan drove $\frac{1}{3}r$ miles in 20 minutes.

ANSWER: $\frac{1}{3}r$ miles