Direction Each of the questions given below consists of a question followed by three statements. You have to study the question and the statements and decide which of the statement(s) is/are necessary to answer the question.
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.

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 and Explanation
Answer:D
Explanation: Let the speed of the train be x metres/sec. Time taken to cross a signal pole = 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 Length of train = 330 m. I and III give, 18 = 330 x = 330 m/sec = 55 m/sec. x 18 3 II and III give, 36 = 2 x 330 x = 660 m/sec = 55 m/sec. x 36 3 Correct answer is (D).
2.

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 and Explanation
Answer: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.)