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 4 of 5.
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?
Janvi said:
1 decade ago
Sorry but I am confuse about this question please can any explain me in detail.
ParthShah said:
1 decade ago
It is very simple. To find out two unknown variable we need two equations. So @Sundar is right.
Raja said:
1 decade ago
@Kausar and @Vivek without knowing the length of the other train how would you find velocity of other train ?
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.
Kausar Shamim said:
1 decade ago
According to me option E is not right as statement II alone is needed to find the speed of the train.
Adsam said:
1 decade ago
II alone sufficient since only the speed of 210m train is asked.
Gagan Mathur said:
1 decade ago
One of the trains speed is given. All we have to do is use the formula time to cross each other = (l1+l2)/(u-v).
A.srikanth said:
1 decade ago
What @Sunder said it is right.
And what @GAUTHM KUMAR said is just like he showing his sense of humor. The answer E is correct.
And coming to @Adithya.
With out knowing the length of second train how you are going to find speed of first train ?
And what @GAUTHM KUMAR said is just like he showing his sense of humor. The answer E is correct.
And coming to @Adithya.
With out knowing the length of second train how you are going to find speed of first train ?
Rakshit said:
1 decade ago
We can find speed by Ist statement by using formula s=d/t
d=300+210=510
t=10 sec
s=51m/sec.
Using relative speed formula we can
S1+S2=D1/T
S1=x
S2=51m/sec
D1=210
T=10 sec.
d=300+210=510
t=10 sec
s=51m/sec.
Using relative speed formula we can
S1+S2=D1/T
S1=x
S2=51m/sec
D1=210
T=10 sec.
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