Question

A motor boat travels 60 miles down a river in three hours but takes five hours to return upstream. Find the rate of the boat in still water and the rate of the current.

Answer 1

• boat: 16 mph
• current: 4 mph

Explanation:

speed = distance / time

The rate downriver is (60 mi)/(3 h) = 20 mi/h.

The rate upriver is (60 mi)/(5 h) = 12 mi/h.

The rate of the boat in still water is the average of these:

(20 +12)/2 mi/h = 16 mi/h

The rate of the current is the difference between the boat speed and actual speed:

16 mi/h - 12 mi/h = 4 mi/h