A crew can row 40 km downstream in 4 hours and 20 km upstream in 5 hours. Find the speed of the stream. MCQ with Answer and Explanation

Explanation:
Let total distance be 100 km. First segment = 30 km; Time = 30 / 15 = 2 hours. Second segment = 70 km; Time = 70 / 35 = 2 hours. Total distance = 100 km, Total time = 4 hours. Average speed = 100 / 4 = 25 km/h.

Explanation:
Speed of sound = Distance / Time = 4080 / 12 = 340 m/s.

Explanation:
New speed = 4/5 of usual speed => New time = 5/4 of usual time. Difference = 1/4 of usual time = 15 minutes. Usual time = 15 * 4 = 60 minutes.