A person row a boat 45 km downstream in 3 hours and manages the return journey upstream in 9 hours. Find the speed of the river current. MCQ with Answer and Explanation
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Question #1
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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.
Correct Answer: Option A
Explanation:
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.
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.
This question belongs to:
Maths
Time Speed and Distance
Question #2
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A train 150 meters long completely passes a stone in 15 seconds. Find the speed of the train in km/h.
Correct Answer: Option B
Explanation:
Speed of train = 150 / 15 = 10 m/s. In km/h = 10 * (18/5) = 36 km/h.
Speed of train = 150 / 15 = 10 m/s. In km/h = 10 * (18/5) = 36 km/h.
This question belongs to:
Maths
Time Speed and Distance
Question #3
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A man covers 1/3 of his total journey at 30 km/h and the remaining 2/3 at 60 km/h. Find his average speed for the entire journey.
Correct Answer: Option B
Explanation:
Let total distance be 90 km. First part = 30 km; Time = 30 / 30 = 1 hour. Remaining part = 60 km; Time = 60 / 60 = 1 hour. Total distance = 90 km, Total time = 2 hours. Average speed = 90 / 2 = 45 km/h.
Let total distance be 90 km. First part = 30 km; Time = 30 / 30 = 1 hour. Remaining part = 60 km; Time = 60 / 60 = 1 hour. Total distance = 90 km, Total time = 2 hours. Average speed = 90 / 2 = 45 km/h.
This question belongs to:
Maths
Time Speed and Distance
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