Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - Data Sufficiency 1 (Q.No. 1)
Directions to Solve
Each of the questions given below consists of a statement and / or a question and two statements numbered I and II given below it. You have to decide whether the data provided in the statement(s) is / are sufficient to answer the given question. Read the both statements and
- Give answer (A) if the data in Statement I alone are sufficient to answer the question, while the data in Statement II alone are not sufficient to answer the question.
- Give answer (B) if the data in Statement II alone are sufficient to answer the question, while the data in Statement I alone are not sufficient to answer the question.
- Give answer (C) if the data either in Statement I or in Statement II alone are sufficient to answer the question.
- Give answer (D) if the data even in both Statements I and II together are not sufficient to answer the question.
- Give answer(E) if the data in both Statements I and II together are necessary to answer the question.
1.
What is the speed of the train whose length is 210 metres? | |
I. | The train crosses another train (Howrah Express/12869) of 300 metres length running in opposite direction in 10 seconds. |
II. | The train crosses another train (Howrah Express/12869) running in the same direction at the speed of 60 km/hr in 30 seconds. |
Answer: Option
Explanation:
| Time taken to cross the train, running in opposite directions |
= | (l1 + l2) | sec. |
| (u + v) |
 10 = |
(210 + 300) |
| (u + v) |
u + v = 51.
| Time taken to cross the train, running in same direction = | (l1 + l2) | sec. |
| (u - v) |
| 30 = |
(210 + 300) |
| (u - 60 x (5/18)) |
| u = |
 |
17 + | 50 |  m/sec. |
| 3 |
Thus, u and v can be obtained.
Correct answer is (E).
Discussion:
45 comments Page 2 of 5.
Vivek kumar said:
1 decade ago
Statement 2 is sufficient to find out the velocity of train having length 210m. So given answer is wrong.
Raja said:
1 decade ago
@Kausar and @Vivek without knowing the length of the other train how would you find velocity of other train ?
ParthShah said:
1 decade ago
It is very simple. To find out two unknown variable we need two equations. So @Sundar is right.
Janvi said:
1 decade ago
Sorry but I am confuse about this question please can any explain me in detail.
Sourav Saha said:
1 decade ago
In the problem using statement I we can find out the sum of the speeds of both the train u+v=51 -- (1) and can't we use the speed of the second train i.e. 60 km/hr and replace it in equation 1?
The results are 103/3 by replacing. And 101/3 by following the method given in the site.
Why is this difference in the result?
The results are 103/3 by replacing. And 101/3 by following the method given in the site.
Why is this difference in the result?
Lokesh said:
1 decade ago
Please anyone explain me. I think the answer is 'D' but it was 'E'. Why?
Utsav Bansal said:
1 decade ago
Option E is okay, just see the instruction guys both statements together are necessary to answer this question as from stat-1 you will get the length of other train n using stat-2 data you can calculate the speed easily, one thing that I find ambiguous is that both statements are contradicting as in 1st one train is moving in opposite direction while in 2nd one same train is moving in same direction.
Udita Mandal said:
10 years ago
Hi, I think correct answer is 'B' because according to the question we have to find out only speed of train with length 210 m i.e. 'u', which can be satisfactorily found out by the information given in option 2, there is no need of finding value of 'v', and none of information given in option 1 is helpful in finding out the answer.
So correct answer according to me is 'B' only option 2 is sufficient to answer the given question. Please go through my suggestion and if I am wrong then correct my doubt.
Thank you!
So correct answer according to me is 'B' only option 2 is sufficient to answer the given question. Please go through my suggestion and if I am wrong then correct my doubt.
Thank you!
M.Homesh said:
9 years ago
We can also solve it by using the relative speed method.
S1 + S2 = D1/T.
S1 + S2 = D1/T.
Shubham said:
9 years ago
Statement 2 is sufficient.
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