A man rows a boat 30 km downstream in 3 hours and returns upstream in 6 hours. Find the speed of the stream. MCQ with Answer and Explanation

Explanation:
Relative speed = 140 / 12 = 35/3 m/s = (35/3) * (18/5) = 42 km/h. Since both walk/move in the same direction, Relative Speed = Speed of train - Speed of pedestrian => 42 = Speed of train - 4 => Speed of train = 46 km/h.

Explanation:
Ratio of speeds = 5:6, so ratio of times taken = 6:5. Slower car takes 6 parts = 3 hours => 1 part = 0.5 hours. Time for faster car = 5 parts = 5 * 0.5 = 2.5 hours.

Explanation:
Time difference = 30 minutes = 0.5 hours. Let distance be d. d / 4 - d / 8 = 0.5 => d / 8 = 0.5 => d = 4 km.