Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - Data Sufficiency 2 (Q.No. 1)
Directions to Solve
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. |
Answer: Option
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).
Discussion:
20 comments Page 2 of 2.
Aswani said:
8 years ago
Yes, answer is d. I agree.
MISHU said:
9 years ago
Crosses the pole in 18 sec (From 1). so, in 18 sec the train goes a length equal to its own length which is 330 ( from 3).
Now, in 18 sec train passes 330 m, so speed = (330/18) = 55/3.
So, the answer : I & III.
Now, in 18 sec train passes 330 m, so speed = (330/18) = 55/3.
So, the answer : I & III.
Santosh pattapu said:
9 years ago
It can be possible for any length of the train.
Let us suppose length be 360.
case I: 18 = 360/x => x = 2.
case II: 36 = 360 * 2/x => x = 2.
So, it can be any length III comes true.
Now as we know I implies II
So, the answer is E
It cannot be A because III comes true in all cases similarly B can't be, C can't be.
If we consider E, it is correct in all cases.
If we consider D, it is representing 2 cases of E so it can also be true.
Let us suppose length be 360.
case I: 18 = 360/x => x = 2.
case II: 36 = 360 * 2/x => x = 2.
So, it can be any length III comes true.
Now as we know I implies II
So, the answer is E
It cannot be A because III comes true in all cases similarly B can't be, C can't be.
If we consider E, it is correct in all cases.
If we consider D, it is representing 2 cases of E so it can also be true.
RahulJ said:
9 years ago
They gave answer correct but forgot option l & lll OR ll & lll.
Satya said:
9 years ago
Any of the 2 can be used because 1 and 2 can also suffice to find the speed of the train.
Dharani natarajan said:
1 decade ago
Thus the speed of the train can be found by the formula (L +l)*s. As per the formula may be 1st and 2nd, 2nd and 3rd are found to be correct.
Technista said:
1 decade ago
I & II can also be used.
We'll get 2 equations. Since length of platform is equal to the length of train. According to me the answer is wrong.
We'll get 2 equations. Since length of platform is equal to the length of train. According to me the answer is wrong.
Gurucharan said:
1 decade ago
Answer given is correct.
They are implying that I&III or I&III can be used but not I and II.
They are implying that I&III or I&III can be used but not I and II.
Vinod Batra said:
1 decade ago
Answer given is wrong because, if we consider only III statement then i.e.
III. Length of the train is 330 metres.
We can not find the speed, by knowing length of the train only.
III. Length of the train is 330 metres.
We can not find the speed, by knowing length of the train only.
Vivek kumar said:
1 decade ago
According to me any 2 of 3 are sufficient to find out the velocity of train. So given answer is wrong.
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