A commuter covers 40% of his total journey distance at 40 km/h and the remaining 60% at 60 km/h. Find his average speed for the whole journey. MCQ with Answer and Explanation
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Question #1
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A thief escapes at 5:00 AM at 40 km/h. The police pursue him starting at 6:00 AM at 50 km/h. At what time will the thief be apprehended?
Correct Answer: Option A
Explanation:
By 6:00 AM, the thief has traveled for 1 hour and covered 40 km. Relative speed = 50 - 40 = 10 km/h. Time taken to catch = 40 / 10 = 4 hours. Capture time = 6:00 AM + 4 hours = 10:00 AM.
By 6:00 AM, the thief has traveled for 1 hour and covered 40 km. Relative speed = 50 - 40 = 10 km/h. Time taken to catch = 40 / 10 = 4 hours. Capture time = 6:00 AM + 4 hours = 10:00 AM.
This question belongs to:
Maths
Time Speed and Distance
Question #2
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A train 120 meters long is running at a speed of 54 km/h. How long will it take to cross a platform 180 meters long?
Correct Answer: Option B
Explanation:
Speed of train = 54 * (5/18) = 15 m/s. Total distance = 120 + 180 = 300 meters. Time taken = 300 / 15 = 20 seconds.
Speed of train = 54 * (5/18) = 15 m/s. Total distance = 120 + 180 = 300 meters. Time taken = 300 / 15 = 20 seconds.
This question belongs to:
Maths
Time Speed and Distance
Question #3
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A car covers four successive 3 km stretches at speeds of 10 km/h, 20 km/h, 30 km/h and 60 km/h respectively. Its average speed for this distance is:
Correct Answer: Option D
Explanation:
Total distance = 4 * 3 = 12 km. Total time = 3/10 + 3/20 + 3/30 + 3/60 = (18 + 9 + 6 + 3)/60 = 36/60 = 0.6 hours. Average speed = 12 / 0.6 = 20 km/h.
Total distance = 4 * 3 = 12 km. Total time = 3/10 + 3/20 + 3/30 + 3/60 = (18 + 9 + 6 + 3)/60 = 36/60 = 0.6 hours. Average speed = 12 / 0.6 = 20 km/h.
This question belongs to:
Maths
Time Speed and Distance
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