Multiple choice

Two trains start at the same time from two stations A and B towards each other. They arrive at B and A respectively in 5 hours and 20 hours after they passed each other. If the speed of the train that started from A is 56 kmph, then what is the speed of the second train (in kmph)?

  1. 28 kmph

  2. 26 kmph

  3. 24 kmph

  4. 22 kmph
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A Correct answer
Explanation

For two objects moving towards each other, the ratio of their speeds is the square root of the inverse ratio of the times taken after meeting: v1/v2 = sqrt(t2/t1). Here, 56/v2 = sqrt(20/5) = sqrt(4) = 2. Thus, v2 = 56 / 2 = 28 kmph.

AI explanation

Using the rule that if two trains start simultaneously and take t1 and t2 hours to reach their destinations after crossing, the ratio of their speeds is the square root of the inverse ratio of their times. So, Speed A / Speed B equals the square root of (Time B / Time A). Substituting the values gives 56 / Speed B equals the square root of (20 / 5), which simplifies to the square root of 4, giving 2. The speed of the second train is 28 kmph.

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