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Discussion :: Problems on Trains

1. What is the speed of the train?

I. The train crosses a signal pole in 18 seconds.

II. The train crosses a platform of equal length in 36 seconds.

III. Length of the train is 330 metres

2.  A. I and II only B. II and III only C. I and III  only D. III and either I or II only E. Any two of the three

Explanation :

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

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

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

Length of train = 330 m.

 I and III give, 18 = $$\frac { 330 } { X }$$ x = $$\frac { 330 } { 18 }$$ m/sec = $$\frac { 55} { 3 }$$m/sec.

 II and III give, 36 = $$\frac { 2 \times 330 } { X }$$    x = $$\frac { 660 } { 36 }$$m/sec = $$\frac { 55 } { 3 }$$m/sec.