Two boats go downstream from point X to point Y. The faster boat covers the distance from X to Y 1.5 times as fast as the slower boat. It is known that for every hour the slower boat lags behind the faster boat by 8 km. However if they go upstream then the faster boat covers the distance from Y to X in half the time as the slower boat. Find the speed of the slower boat in still water?

Because the faster boat goes downstream 1.5 times as fast as the slower boat, the difference in their downstream speeds is 8 km/h, making the slower boat's downstream speed 16 km/h and the faster boat's 24 km/h. Going upstream, the faster boat takes half the time, meaning its upstream speed is twice the slower boat's upstream speed; setting the slower boat's still water speed as u and stream speed as v gives u plus v equals 16 and 24 minus v equals 2 times u minus v. Solving this system of equations results in a still water speed of 12 km/h for the slower boat.

• Thanks
• Wrong explanation