A boat can row 11 km/h in still water and the velocity index of the current stream is 3 km/h. Find the time span taken to row 32 km upstream. MCQ with Answer and Explanation
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Question #1
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The speed of a train is 25% more than the speed of a car. Both start from city P at the same time and reach city Q, 150 km away, at the same time. On the way, the train stops for 15 minutes at various stations. What is the speed of the car?
Correct Answer: Option A
Explanation:
Let car speed be c, then train speed is 1.25c. Time difference = 150/c - 150/(1.25c) = 15/60 hour = 1/4 hour. 150/c * (1 - 1/1.25) = 1/4 => 150/c * (0.25/1.25) = 1/4 => 150/c * (1/5) = 1/4 => 30/c = 1/4 => c = 120 km/h.
Let car speed be c, then train speed is 1.25c. Time difference = 150/c - 150/(1.25c) = 15/60 hour = 1/4 hour. 150/c * (1 - 1/1.25) = 1/4 => 150/c * (0.25/1.25) = 1/4 => 150/c * (1/5) = 1/4 => 30/c = 1/4 => c = 120 km/h.
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Maths
Time Speed and Distance
Question #2
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Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train is 120 meters, in what time will they cross each other traveling in opposite directions?
Correct Answer: Option D
Explanation:
Speed of first train = 120 / 10 = 12 m/s. Speed of second train = 120 / 15 = 8 m/s. Total distance to cross each other = 120 + 120 = 240 meters. Relative speed in opposite directions = 12 + 8 = 20 m/s. Time = 240 / 20 = 12 seconds.
Speed of first train = 120 / 10 = 12 m/s. Speed of second train = 120 / 15 = 8 m/s. Total distance to cross each other = 120 + 120 = 240 meters. Relative speed in opposite directions = 12 + 8 = 20 m/s. Time = 240 / 20 = 12 seconds.
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Maths
Time Speed and Distance
Question #3
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If a delivery agent cycles at 15 km/h instead of 11 km/h, he travels 20 km more in the same allotted duration. Find the actual distance covered by him at his lower speed.
Correct Answer: Option B
Explanation:
Let the time duration be t hours. Distance difference = 15t - 11t = 4t = 20 km => t = 5 hours. Distance covered at lower speed = 11 * 5 = 55 km.
Let the time duration be t hours. Distance difference = 15t - 11t = 4t = 20 km => t = 5 hours. Distance covered at lower speed = 11 * 5 = 55 km.
This question belongs to:
Maths
Time Speed and Distance
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