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Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - Data Sufficiency 1 (Q.No. 3)
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.
3.

What is the length of a running train?

I. 

The train crosses a man in 9 seconds.

 II. 

The train crosses a 240 metre long platform in 24 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 by train to cross a man = Length of train       Speed = l ....(i)
Speed of train 9

Time taken by train
to cross a platform =		 (Length of train +
Length of platform)		      Speed = l + 240 ....(ii)
Speed of train 24

From (i) and (ii), we get l = l + 240 .
9 24

Thus, l can be obtained. So both I and II are necessary to get the answer.

The correct answer is (E).

Discussion:
16 comments Page 2 of 2.
Sana said:   7 years ago
Man is stationary & speed of the train is same for passing both man and platform. Thatswhy we can equate the two equations and get the length. It comes to be 144 meters.
Atul said:   7 years ago
How can we say the train crossing the man and the platform is same. Also, the speed is also same. If nothing is given how option E is correct. Please specify in the question if any assumption is to be made or not.
Sujata said:   7 years ago
How can we say that the speed of train to cross man and platform is same?

Please anyone explain?
Andy said:   6 years ago
x/9 = x+240/24.
24x = 9x + 2160.
15x = 2160.
x = 144.
(4)
Anty said:   6 years ago
x/9 = x+240/24.
24x = 9x + 2160.
15x = 2160.
x = 144.
(4)
Somil kumar bhadula said:   3 years ago
@All.

Here is the answer.

l/9 = l + 240/24,
l/9 = 9(l+10),
l/9 = 9l + 90,
10l = 91.
L= 91/10.
L = 9.5.
So, Answer is 9.5.
(2)
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