Given below is a question followed by three statements. Identify the statement or statements necessary to answer the question: what is the speed of the train?

1.The train crosses another train running in the opposite direction in 20 seconds

2.The train crosses a platform of length 300 m in 30 seconds

3.The train crosses a pole in 10 seconds

AI and II only

BI and III only

CII and III only ✓ Correct

D1, 2, 3

Correct answer: (C) II and III only

Explanation

Statement 2 and Statement 3 together fix the train's speed.

Statement 3 gives length L = speed x 10, since a pole crossing needs only the train's length.

Statement 2 gives L + 300 = speed x 30 for the platform crossing.

Substituting L = 10v : 10v + 300 = 30v, so 20v = 300.

This yields v = 15 m/s, so both these statements are needed.

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