A person can row 8 km/h in still water. He finds that it takes him thrice as long to row upstream as to row downstream. Find the speed of the current. MCQ with Answer and Explanation

Explanation:
Downstream speed = 40 / 4 = 10 km/h. Upstream speed = 20 / 4 = 5 km/h. Speed in still water = (10 + 5) / 2 = 7.5 km/h.

Explanation:
Speed of train = 72 * (5/18) = 20 m/s. Total distance = 160 + 240 = 400 meters. Time taken = 400 / 20 = 20 seconds.

Explanation:
Let the required speed for the second half be x km/h. Using the average speed formula for equal halves: Average Speed = 2v1*v2 / (v1 + v2) => 50 = (2 * 40 * x) / (40 + x) => 50(40 + x) = 80x => 2000 + 50x = 80x => 30x = 2000 => x = 66.67 km/h.