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?

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.

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).

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.)

What is the speed of the train?

I. The train crosses 300 metres long platform in 21 seconds.

II. The train crosses another stationary train of equal length in 19x(1/2) seconds.

III. The train crosses a signal pole in 9x(3/4) seconds.

A.	I and II only
B.	I and either II or III only
C.	II and either I or II only
D.	III and either I or II only
E.	None of these.

Answer: Option B

Explanation:

Let the speed of the train be x m/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

I gives, 21 = (l + 300)/x;

II gives, 39/2 = 2l/x;

III gives, 39/4 = l/x.

Thus, (I and II) or (I and III ) give x.

Correct answer is (B)

Q&A What

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?

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