A train 120 meters long passes an active crossing signal point in 6 seconds flat. Find the time interval needed to clear a station platform 240 meters long. MCQ with Answer and Explanation
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Question #1
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A person travels a distance of 24 km at a speed of 6 km/h, another 24 km at 8 km/h and a third 24 km at 12 km/h. Find his average speed for the whole journey.
Correct Answer: Option B
Explanation:
Total distance = 24 + 24 + 24 = 72 km. Total time = 24/6 + 24/8 + 24/12 = 4 + 3 + 2 = 9 hours. Average speed = 72 / 9 = 8 km/h.
Total distance = 24 + 24 + 24 = 72 km. Total time = 24/6 + 24/8 + 24/12 = 4 + 3 + 2 = 9 hours. Average speed = 72 / 9 = 8 km/h.
This question belongs to:
Maths
Time Speed and Distance
Question #2
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A vehicle runs at 30 km/h for 3 hours and 60 km/h for the next 2 hours. Find the average speed for the whole journey.
Correct Answer: Option D
Explanation:
Distance 1 = 30 * 3 = 90 km. Distance 2 = 60 * 2 = 120 km. Total distance = 210 km. Total time = 3 + 2 = 5 hours. Average speed = 210 / 5 = 42 km/h.
Distance 1 = 30 * 3 = 90 km. Distance 2 = 60 * 2 = 120 km. Total distance = 210 km. Total time = 3 + 2 = 5 hours. Average speed = 210 / 5 = 42 km/h.
This question belongs to:
Maths
Time Speed and Distance
Question #3
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A man can row 9 km/h in still water. He rows to a place 24 km away and back in a total of 6 hours. Find the speed of the river current.
Correct Answer: Option B
Explanation:
Let speed of current be c. 24 / (9 + c) + 24 / (9 - c) = 6. Dividing by 6: 4 / (9 + c) + 4 / (9 - c) = 1 => 4(9 - c + 9 + c) = 81 - c^2 => 72 = 81 - c^2 => c^2 = 9 => c = 3 km/h.
Let speed of current be c. 24 / (9 + c) + 24 / (9 - c) = 6. Dividing by 6: 4 / (9 + c) + 4 / (9 - c) = 1 => 4(9 - c + 9 + c) = 81 - c^2 => 72 = 81 - c^2 => c^2 = 9 => c = 3 km/h.
This question belongs to:
Maths
Time Speed and Distance
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