A boat travels 24 kilometers downstream in 4 hours, while it takes 6 hours to cover the same distance upstream. What is the speed of the boat in still water?

Explanation

The downstream speed is 24 km ÷ 4 hrs = 6 km/hr, and the upstream speed is 24 km ÷ 6 hrs = 4 km/hr. The boat's speed in still water is the average of these two speeds: (6 + 4) ÷ 2 = 5 km/hr, which does not match any of the provided options.