What is the speed of the train the train crosses a signal pole in 18 seconds the train crosses a platform of equal length in 36 seconds length of the train is 330 meters?

Answer & Explanation

Answer: Option D

Explanation:

Let the speed of the train be x m/sec.

III gives that the men are moving in the same direction.

I gives, time taken to pass a man = $$\frac{l}{(x - 3 * \frac{5}{18})}$$

= ($$\frac{6l}{6x - 5}$$)sec.

$$\therefore$$ $$\frac{6l}{6x - 5}$$ = 9

=> 54x - 6l = 45

=> 18x - 2l = 15 ...(i)

II gives, time taken to pass another man = $$\frac{l}{(x - 6 * \frac{5}{18})}$$sec

= $$\frac{3l}{(3x - 5)}$$sec.

$$\therefore$$ $$\frac{3l}{(3x - 5)}$$ = 10

=> 30x - 3l = 50 . . .(i)

On solving (i) and (ii), we get : x = $$\frac{55}{6}$$m/sec.

Thus, all I, II, III are needed to get the answer.

Question 51 . What is the speed of the train?1. The train crosses a signal pole in 13 seconds2. The train crosses a platform of length 250 meters in 27 seconds3. The train crosses another train running in the same direction in 32 seconds

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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: Option 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). View Answer | Workspace | Report | Discuss in Forum

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: 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 13x + 250 = 27 x x = 125 m/sec. 7 Thus I and II give the speed of the train. The correct answer is (A.) View Answer | Workspace | Report | Discuss in Forum