Aptitude - Problems on Trains - Discussion

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.

2. 

What is the length of a running train crossing another 180 metre long train running in the opposite direction?

I. 

The relative speed of the two trains was 150 kmph.

 II. 

The trains took 9 seconds to cross each other.

[A]. I alone sufficient while II alone not sufficient to answer
[B]. II alone sufficient while I alone not sufficient to answer
[C]. Either I or II alone sufficient to answer
[D]. Both I and II are not sufficient to answer
[E]. Both I and II are necessary to answer

Answer: Option E

Explanation:

Let the two trains of length a metres and b metres be moving in opposite directions at u m/s and v m/s.

Time taken to cross each other = (a + b) sec.
(u + v)

Now, b = 180, u + v = 150 x 5 m/sec = 125 m/sec.
18 3

9 = a + 180
(125/3)

a = (375 - 180) = 195 m.


Aditi said: (Nov 30, 2010)  
what is 5/18 in (u+v)?

Kapil said: (Dec 16, 2010)  
Relative speed,u+v = 150 km/hr
we multiply it with 5/18 to convert it into m/sec
u+v= 150*(5/18)

Sanjay said: (Jun 17, 2012)  
@ADITI.

1 kilo is 1000.

1hour is 60s*60m=3600s.

1000/3600 = 5/18.

If you multiply 5/18 to that value you can convert it in to m/s.

Rakhee said: (May 16, 2016)  
How 9 comes? I am not getting this please help me.

Mukesh said: (Aug 9, 2016)  
Time is taken to cross each other 9 seconds given in the question. So we can put the value in that place in the formula.

Muhammad Safad said: (Oct 1, 2016)  
What mentioned u and v?

Soni said: (Nov 8, 2016)  
I am not getting this answer. Please explain it.

Dilhara said: (Feb 19, 2017)  
What is u+v?

Please explain it.

Ramshya Fathima said: (May 16, 2017)  
How we take b=180?

I don't understand please explain anyone to know the answer.

Saumya said: (Aug 13, 2017)  
Relative speed means U-V but it is considering u+v.

So, the given answer is wrong.

Nur Alom said: (Aug 25, 2017)  
The relative speed for opposite direction is u+v not u-v.

Naeem said: (Sep 19, 2017)  
@Dilhara.

u+v relative speed in case of opp. direction.

@Ramshya_Fathima b=180 is given in data. Check it.

Sony Sharda said: (Mar 3, 2018)  
How we take b=180?

Deepanshu said: (Jun 4, 2018)  
@Sony Sharda.

B is the length of another train which is given in the question=180m.

Jagannath said: (Sep 5, 2018)  
Length of the train = speed* time.

Shweta said: (Jan 23, 2019)  
How come 125/3? Please explain.

Sunitha said: (Mar 6, 2019)  
@All.

When you multiply 150*5/18 then you will get 125/3.

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