A man rows a boat 800 feet upstream against a constant current in 16 minutes.

Question

A man rows a boat 800 feet upstream against a constant current in 16 minutes. He then rows 480 feet downstream (with the same current) in 8 minutes. Find the speed of the current and the equivalent rate at which he can row in still water.

speed of current	ft/min
speed of boat in still water	ft/min

Answer 1

Upstream, 800 ft/16 min = 50 ft/min

Downstream, 480 ft/8 min = 60 ft/min

Let s be the speed in still water and c be the current.

Then, speed upstream is s - c = 50

speed downstream is s + c = 60

s - c = 50

s + c = 60

Adding, 2s = 110

s = 55

s + c = 60

55 + c = 60

c = 5

speed of current = 5 ft/min

speed of boat in still water = 55 ft/min