Aptitude - Problems on Trains
- Problems on Trains - Formulas
- Problems on Trains - General Questions
- Problems on Trains - Data Sufficiency 1
- Problems on Trains - Data Sufficiency 2
- Problems on Trains - Data Sufficiency 3
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.)