A train X travelling at 15 m sec crosses another train Y travelling in opposite direction at 72 kmph...........

Qunatitative Aptitude (RBI Ast) Time & distance

A train X travelling at 15 m/sec crosses another train Y travelling in opposite direction at 72 kmph in 15 seconds. Find the length of train X which is twice of that of train Y?

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RBI Assistant 2020

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400 m

300 m

350 m

450 m

500 m

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Explanation:

- Train X and train Y are moving in opposite directions. Relative speed needs to be calculated.

- Convert train Y's speed from kmph to m/sec: \(72 \, \text{kmph} = 72 \times \frac{1000}{3600} = 20 \, \text{m/sec}\).

- Relative speed of X and Y together = \(15 \, \text{m/sec} + 20 \, \text{m/sec} = 35 \, \text{m/sec}\).

- They cross each other in 15 seconds. Total distance covered in crossing = \(35 \, \text{m/sec} \times 15 \, \text{seconds} = 525 \, \text{meters}\).

- Let length of train Y = \(L\), then length of train X = \(2L\).

- \(2L + L = 525\), thus \(3L = 525\).

- Solve for \(L\): \(L = 175 \, \text{m}\).

- Length of train X = \(2 \times 175 \, \text{m} = 350 \, \text{m}\).

- Option 3: 350 m is correct.