A sailboat travels 48 miles upstream in 6 hours and return back downstream in 4 hours. What is the speed of the boat in still water?

Let s be the speed of the boat in still water.

Let c be the speed of the current.

s - c = 48/6 = 8

s + c = 48/4 = 12

Adding the two equations, we get:

2s = 20

s = 10

The answer is 10 miles per hour.