Julie and Eric row their boat (at a constant speed) 21 miles downstream for 3 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 7 hours. Find the rate of the current.

Answer 1

Their speed downstream = 21/3 = 7mph
Their speed upstream = 21/7 = 3mph

So, the river speed is (7-3)/2 = 2mph

Their rowing speed is 5mph.