A boat travels for three hours with a current of 3 mph and then returns the same distance against the current in four hours. What is the boat's speed in still water? How far did the boat travel one way?

Answer

A) 21 mph, 72 miles

B) 12 mph, 24 miles

C) 16 mph, 36 miles

D) 24 mph, 48 miles

Solution:

the boat's speed in still water: x

The speed with current: (x+3)

The speed against current: (x-3)

The equation is

3(x+3) = 4(x-3)

x = 21 mph

The distance = 3*(21+3)= 72 miles

We choose (A)