A Coast-Guard patrol boat travels 4 hr on a trip downstream with a 6-mph current. The return trip against the same current

Question

takes 5 hr. Find the speed of the boat in still water

Answer 1

The downstream speed with respect to land is V+6 and the upstream speed is V-6, where V is the speed in still water.
Let the distance be D

D/(V+6) = 4 hrs
D/(V-6) = 5

4(V+6) = 5(V-6)
V = 54 mph