Between two stations, a train accelerates uniformly at first, then moves with constant speed and finally retards uniformly. If the ratios of time taken are 2:1:2 and the greatest speed is 10 km/hr, find the average speed over the whole journey.
A
6km/hr
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B
9km/hr
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C
4.5km/hr
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D
3km/hr
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Solution
The correct option is A6km/hr Let, the time taken to travel second part of the journey be t, where the train accelerates with constant acceleration.
Since, the ratio of the times are 2:1:2 so, the time taken to travel the part of the journey is 2t and time taken to the third part of the journey is 2t.