Multiple choice

What is the speed of train X? (I) Train X crosses another 200 m long train in 6 seconds. (II) The speed of another train is 80 km/hr. (III) The length of train X is half of the length of another train.

  1. Only I and II

  2. Only II and III

  3. Only I and III

  4. All

  5. Answer can't be given even using all the three statements.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

From I and III: Train X length = 200/2 = 100m. Train X crosses 200m train in 6 seconds. Relative speed = (100 + 200)/6 = 50 m/s = 180 km/hr. But we don't know if trains are moving in same or opposite direction. Statement II gives other train's speed as 80 km/hr, but without direction, we cannot find train X's speed (could be 180-80=100 or 180+80=260 km/hr). The answer cannot be determined uniquely.

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