Sailing with the current, a boat takes 3 hours to travel 48 miles. The return trip, against the current, takes 4 hours. How do you find the average speed of the boat for the entire trip and the speed of the current?
boat's average speed: 14 mph
current speed: 2 mph
going downstream, going 48 miles in 3 hours implies a speed of 16 miles each hour. (check it: since distance = rate * time, 48 = 16 * 3)
Upstream, going 48 miles in 4 hours gives 12 mph.
So, 14 mph is the speed the boat makes through the water, or the speed it would have if there was NO current.
The current speed, added to this basic speed, gives you 16 mph going downstream, and 12 going up stream. So, this is necessarily 2 mph.