1. 

What is the length of a running train?

I. The train crosses a man in 9 seconds.

II. The train crosses a 240 metre long platform in 24 seconds.

A. I alone sufficient while II alone not sufficient to answer
B. II alone sufficient while I alone not sufficient to answer
C. Either I or II alone sufficient to answer
D. Both I and II are not sufficient to answer
E. Both I and II are necessary to answer

Answer: Option E

Explanation:

Time taken by train to cross a man :

= Length of train       Speed = l ....(i)
Speed of train 9

Time taken by train to cross a platform :

= (Length of train +
Length of platform)
     Speed = l + 240 ....(ii)
Speed of train 24

From (i) and (ii), we get l = l + 240 .
9 24

Thus, l can be obtained. So both I and II are necessary to get the answer.

The correct answer is (E).