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 1 of 2.
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.
Ganadakshaka.k said:
5 years ago
As statement 1 and 3 can be used because time and train length is given calculated by this formula:t = l/s.
And 2 and 3 can be used because of the same reason t=2*l/s, 2is multiplied because in question they have given train and platform length are same.
So, answer D is correct.
And 2 and 3 can be used because of the same reason t=2*l/s, 2is multiplied because in question they have given train and platform length are same.
So, answer D is correct.
(2)
Shubham said:
8 years ago
Guys, who are saying statement 1 and 2 is also sufficient. Kindly, solve it once, you will see, both LHS and RHS will come out equal, and we won't get any result. That's why statement 3 and any of statement 1 or 2 is the right answer.
(2)
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.
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.
Anchal said:
6 years ago
The answer must be E.
If used 1 and 2 only. Then their velocities are equal and hence after finding the value of train length easily speed can be found out.
If used 1 and 2 only. Then their velocities are equal and hence after finding the value of train length easily speed can be found out.
(4)
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.
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.
Anksuh said:
6 years ago
@All.
By comparing 1 & 2 speed becomes length/18 in both cases so we can't solve them. Therefore given option is correct.
By comparing 1 & 2 speed becomes length/18 in both cases so we can't solve them. Therefore given option is correct.
(1)
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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