A train of length $150$ m crosses a $250$ m long bridge in $20$ seconds. The speed of the train (in km/h) is:

A train of length $150$ m crosses a $250$ m long bridge in $20$ seconds. The speed of the train (in km/h) is:
  1. $54$
  2. $60$
  3. $72$
  4. $75$

Solution

Total length $= 400$ m, time $= 20$ s. Speed $= 20$ m/s $= 20 \times \dfrac{18}{5} = 72$ km/h.

Asked in: IMO

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