Multiple choice

A train passes two bridges of lengths 500 m and 250 m in 100 seconds and 60 seconds, respectively. Find the length of the train.

  1. 125 metres

  2. 1375 metres

  3. 105 metres

  4. 150 metres

  5. None of These
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let L be the train length and v be the speed. (L + 500)/100 = v and (L + 250)/60 = v. Equating them: (L + 500)/100 = (L + 250)/60. Simplifying, 6(L + 500) = 10(L + 250), so 6L + 3000 = 10L + 2500. 4L = 500, L = 125.

AI explanation

Let the length of the train be L and its speed be S. Using the distance formula for the first bridge, L plus 500 equals 100S. For the second bridge, L plus 250 equals 60S. Subtracting the second equation from the first gives 250 equals 40S, meaning the speed S is 6.25 m/s. Substituting this speed back into the second equation gives L plus 250 equals 60 times 6.25, so L plus 250 equals 375 and L equals 125. The length of the train is 125 metres.

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