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Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - Data Sufficiency 1 (Q.No. 1)
Problems on Trains
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.

I alone sufficient while II alone not sufficient to answer
II alone sufficient while I alone not sufficient to answer
Either I or II alone sufficient to answer
Both I and II are not sufficient to answer
Both I and II are necessary to answer
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.
Mandal said:   7 years ago
How is statement 2 sufficient? can anyone explain it in details that only statement 2 is sufficient?
(1)
Ramesh Kumar said:   5 years ago
Option E is correct. Because both statements are required for finding out the speed of both trains.

Thanks @Sundar and @Hari.
(1)
Nisha Thakkar said:   1 year ago
@All.

We can directly find the speed of the first train by using the formula speed of the first train = relative speed + speed of the second train.

So, statement B alone is sufficient, therefore option B is right.
(1)
Anuj said:   9 years ago
Actually, I have a doubt on this question a tree and having a length of 350 metre cross the bridge length 750 m. If the speed of the train is 55 kilometre per hour how much time will the train take to cross the bridge?

Can anyone solve this?
Vishal saini said:   3 years ago
Both I and II are necessary to answer.

Because statement I is needed to find the II statement.

Through this, we can find the speed of the train which we have to find.
Vinayak N Kamath said:   7 years ago
As they have asked about the speed of train that is 210m long. So data 2 is sufficient to answer.
Shanthkumar said:   7 years ago
Considering the direction of trains as per statement 1 i.e. opposite direction and statement 2 i.e the same direction so we need both statements to find train speed in both directions respectively.
Utkarsh saxena said:   7 years ago
Option E is correct because the length of the second train that is 300 m is given in statement 1 without it you cannot find the answer.
Rathod said:   8 years ago
u=606/5 not (17+50/3=101/3 it is not right).
Sakshi Amrutkar said:   8 years ago
In the above given question where the length of a train is mentioned? please explain about it.
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