A train travels the distance between stations P and Q at a speed of 126 km/h, while in the opposite direction it comes back at 90 km/h. Another train travels the same distance at the average speed of the first train. The time taken by the second train to travel 525 km is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e 5 hours.
| Understanding | Application |
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Average speed = Total distance/Total time Let the distance between P and Q is D. Total distance= D + D = 2D As we know Speed = Distance / Time So, Time = Distance / Speed S1 = 126 km/h S2 = 90 km/h |
Time taken by the first train to travel P to Q (T1)= D/126 Time taken by the first train to travel Q to P(T2) = D/90 Total time = T1 + T2 Total time = (D/126) + (D/90) = 12D/630 Average speed of the train = 2D/(12D/630) = 105 km/hr Speed of the second train = Average speed of first train = 105 km/h Time taken by second train = Distance / Speed = 525 / 105 = 5 hours |