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### Discussion :: Problems on Trains

1. What is the speed of the train?

I. The train crosses a tree in 13 seconds.

II.The train crosses a platform of length 250 metres in 27 seconds.

III. The train crosses another train running in the same direction in 32 seconds.

2. A.
 I and II only
B.

II and III only

C.

I and III only

D.

Any two of the three

E.

None of these

Answer : Option A

Explanation :

Let the speed of the train be x metres/sec.

 Time taken to cross a tree = $$\frac { Length of the train } { Speed of the train }$$

 Time taken to cross a platform = $$\frac { (Length of the train + Length of the Platform) } { Speed of the train }$$

 I gives, 13 = $$\frac { l } { X }$$    13x.

 II gives 27 = $$\frac { l+250 } { X }$$

 $$\frac { 13X +250 } { X }$$= 27

 x = $$\frac { 125 } { 7 }$$m/sec.

Thus I and II give the speed of the train.

The correct answer is (A.)

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