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.

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 4 of 5.

Shanthkumar said:   6 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.

Vinayak N Kamath said:   6 years ago
As they have asked about the speed of train that is 210m long. So data 2 is sufficient to answer.

Mandal said:   6 years ago
How is statement 2 sufficient? can anyone explain it in details that only statement 2 is sufficient?
(1)

Akash C P said:   6 years ago
We are not using the relation u+v=51 to find the final answer so statement 2 alone is sufficient, option B is right.
(6)

Amit Kumar said:   6 years ago
Anuj it will take 0.02 hours to cross the Bridge.
(1)

Nishanth Mekala said:   6 years ago
The speed of the train can be retrieved from statement 2 alone.
(10)

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)

Atchukola Naresh said:   4 years ago
Since in both statement reveals that the another train is "Howrah Express/12869" and its length is 300 meters.

Therefore, we can find the answer with I and II.

If it is not specified (if not included the another trains details specifically) , it may be different trains and different length. In this case, the answer will be "Both I and II are not sufficient to answer".

Hope this will help you a little bit.
(4)

Rakkesh s said:   3 years ago
Statement 1 is not sufficient because we don't know the value of both u&v right in the statement.
(7)

Vishal saini said:   2 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.


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