Data Sufficiency 2
Practice and master this topic with our carefully crafted questions.
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.
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.
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.)
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.
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)