A man covers 3/5 of his journey at 60 km/h, 1/4 of his journey at 40 km/h and the remaining journey at 20 km/h. Find his average speed for the whole transaction. MCQ with Answer and Explanation
A man covers 3/5 of his journey at 60 km/h, 1/4 of his journey at 40 km/h and the remaining journey at 20 km/h. Find his average speed for the whole transaction.
A. 46.15 km/h
B. 44.44 km/h
C. 48.00 km/h
D. 42.5 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let total distance be 400 km. First part = 240 km; Time = 240/60 = 4 hours. Second part = 100 km; Time = 100/40 = 2.5 hours. Remaining distance = 400 - 240 - 100 = 60 km; Time = 60/20 = 3 hours. Total time = 4 + 2.5 + 3 = 9.5 hours. Average speed = 400 / 9.5 = 4000 / 95 = 46.15 km/h.
Explanation:
Speed of the second train = 300 / 3 = 100 km/h. Speed ratio is 4:5, so 5 parts = 100 km/h => 1 part = 20 km/h. Speed of the first train = 4 parts = 4 * 20 = 80 km/h.
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