At full throttle, the boat went upstream 32 miles in 8 times the time it took to go downstream 32 miles at full throttle. If the current was 7 miles per hour, what is the speed of the boat in still water ?

Solution:

The speed of the boat in still water is x

So

8 = (x+7)/(x-7)

x=9

So the speed of the boat in still water is 9 mph