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.
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 = Length of the train
Speed of the train

Time taken to cross a platform

= (Length of the train + Length of the Platform)
Speed of the train

I gives, 13 = l     13x.
x

II gives 27 = l + 250
x

13x + 250 = 27
x

x = 125 m/sec.
7

Thus I and II give the speed of the train.

The correct answer is (A.)