Discussion :: Problems on Trains

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
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 
Answer : Option D
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.  
Correct answer is (D)
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