Solve the problem.
-Julie and Eric row their boat (at a constant speed)45 miles downstream for 5 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 9 hours. Find the rate of the current.
A)2 mph
B)1.5 mph
C)3 mph
D)7 mph

Question

Quizplus · Accepted Answer

The rate of the current can be found by first determining the speed of the boat in still water and the effective speed downstream and upstream. Downstream speed = 45 miles / 5 hours = 9 mph. Upstream speed = 45 miles / 9 hours = 5 mph. The boat's speed in still water is the average of these two speeds, (9 + 5) / 2 = 7 mph. The current's speed is the difference between the boat's speed in still water and its speed upstream or downstream, so (9 - 7) = 2 mph or (7 - 5) = 2 mph.

Solve the Problem. -Julie and Eric Row Their Boat (At a Constant Speed)45