Question

a river flows 4 miles per hour what is the rate in minutes per hour

Answer 1

The unit rate for any quantity of time is 60 minutes per hour.

Answer 2

Your answer will be 60 min per hr because in an hr there are 60 mins, and they are asking you to find the rate in min per hr. 1 hr = 60 min, so again, your answer to this question will be 60 min per hr.   

Hope I helped ya!! xD