Solve.
-A cruise boat travels 72 miles downstream in 4 hours and returns to its starting point upstream in 6 hours. Find the speed of the stream.
A)33 mph
B)3 mph
C)15 mph
D)18 mph

Question

Quizplus · Accepted Answer

The speed of the stream can be found by first determining the speed of the boat in still water and the effective speed downstream and upstream. Downstream speed = distance/time = 72 miles / 4 hours = 18 mph. Upstream speed = 72 miles / 6 hours = 12 mph. The speed of the boat in still water is the average of these two speeds, (18 mph + 12 mph) / 2 = 15 mph. The speed of the stream is the difference between the boat's speed in still water and upstream or downstream speed, which is (18 mph - 15 mph) or (15 mph - 12 mph) = 3 mph.

Solve. -A Cruise Boat Travels 72 Miles Downstream in 4 Hours