It takes a boat 3 hours to travel down a river from point A to point B, and 5 hours to travel up the river from B to A. How long would it take the same boat to go from A to B in still water?
Choose the most appropriate option:
A) 1h 15m  B) 6h 35m  C) 3h 45m  D) 2h 49m  E) 4h 40m
Let: S be the speed of the boat in still water, r be the rate of the water current and d the distance between A and B.   d = 3(S + r) : boat traveling down river   d = 5(S - r) : boat traveling up river   3(S + r) = 5(S - r)   r = S / 4 : solve above equation for r   d = 3(S + S/4) : substitute r by S/4 in equation B   d / S = 3.75 hours = 3 hours and 45 minutes.   correct answer is :3h 45m) 3h 45m
<result>C</result>
It takes a boat 3 hours to travel down a river from point A to point B, and 5 hours to travel up the river from B to A. How long would it take the same boat to go from A to B in still water?