find the average speed of the boat relative to the water

Question

Meg rode her boat upstream a distance of 72 miles and then rowed back to the starting point. The total time of the trip was 18 hours. If the rate of the current was 3 mph, find the average speed of the boat relative to the water

Answer 1

Since water slows down the boat going upstream & speeds up the boat going downstream by the same speed of 3 mph, the average speed of the boat relative to the water would be the same as the average speed of the boat without the water current. That would (72 miles + 72 miles)/18 hours which is 8 mph.