A boat travels upstream for 30 minutes to reach a beach. The same trip traveling downstream takes 20 minutes. If the current is 4 miles per hour and the speed of the boat is constant, find the speed of the boat without any current.
Let the speed of the boat in stillwater =S
30[S - 4] =20[S + 4], solve for S
S = 20 mph - its speed in stillwater.