It takes a barge 1 hour to travel 8 miles downstream with the current and 4 hours to return against the current. Find the speed of the barge in still water and the speed of the current.
A) barge: 8 mph; current: 2 mph
B) barge: 5 mph; current: 3 mph
C) barge: 6 mph; current: 4 mph
D) barge: 6 mph; current: 3 mph

Question

Quizplus · Accepted Answer

The speed of the barge in still water is the average of its speed downstream and upstream. Downstream speed is 8 miles/hour, and upstream speed is 8 miles / 4 hours = 2 miles/hour. The average speed in still water is (8 + 2) / 2 = 5 miles/hour. The speed of the current is the difference between the barge's speed in still water and its speed upstream, or the difference between its speed in still water and its speed downstream, divided by 2. So, the current's speed is (8 - 2) / 2 = 3 miles/hour.

It Takes a Barge 1 Hour to Travel 8 Miles