Discussion :: Problems on Trains

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.
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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