Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 11)
11.
A 270 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the length of the other train?
Answer: Option
Explanation:
Relative speed = (120 + 80) km/hr
| = |  |
200 x | 5 |  m/sec |
| 18 |
| = | |
500 | m/sec. |
| 9 |
Let the length of the other train be x metres.
| Then, | x + 270 | = | 500 |
| 9 | 9 |
x + 270 = 500
x = 230.
Discussion:
66 comments Page 1 of 7.
Meenu said:
2 decades ago
In this solution how you are multiplying 5/18 with 200.
I can't understand that wll you please explain me that.
I can't understand that wll you please explain me that.
Ajantha said:
2 decades ago
Hi meenu,
Total speed(Relative speed) of two trains=120+80=200km/hr
we derived this from km/hr to meter/sec
=200*5/18 (bcas1000/3600=5/18)
=1000/18
=500/9
Total speed(Relative speed) of two trains=120+80=200km/hr
we derived this from km/hr to meter/sec
=200*5/18 (bcas1000/3600=5/18)
=1000/18
=500/9
Pavan said:
1 decade ago
Why you add X and 270 ?
Randhir said:
1 decade ago
If two trains of length a metres and b metres are moving in opposite directions at u m/s and v m/s, then:
The time taken by the trains to cross each other =(a+b)/(u+v)
Then time is 9 sec, a=270 metres, b=x metres, u=120 kmph,
v=80 kmph
Therefore 9=(270+x)/(120+80)*5/18
we multiply (120+80) by 5/18 because converting kmph into m/sec
5/18*200*9=270+x
x=230
The time taken by the trains to cross each other =(a+b)/(u+v)
Then time is 9 sec, a=270 metres, b=x metres, u=120 kmph,
v=80 kmph
Therefore 9=(270+x)/(120+80)*5/18
we multiply (120+80) by 5/18 because converting kmph into m/sec
5/18*200*9=270+x
x=230
Arulmozhi said:
1 decade ago
Hai friends,
Having any other shortcut method to this problem?
Having any other shortcut method to this problem?
Pankaj kumar marskole said:
1 decade ago
Time taken crossed the train=length of the both train/length of the speed.
Let length of the 2nd train is x.
9= (270+x)/(100/3+200/9).
X=230.
Let length of the 2nd train is x.
9= (270+x)/(100/3+200/9).
X=230.
Yogesh said:
1 decade ago
Pleas let me know, where 100/3 comes from ?
Nareen said:
1 decade ago
Short cut Method
Relative speed = (120 + 80) km/hr
= 200 x 5/18 m/sec
= 500/9 m/sec.
= 500/9*9
= 500 m
= u+v = 500
= 270+v = 500
= 230m
Relative speed = (120 + 80) km/hr
= 200 x 5/18 m/sec
= 500/9 m/sec.
= 500/9*9
= 500 m
= u+v = 500
= 270+v = 500
= 230m
Pramod said:
1 decade ago
Two trains are in opposite travelling in the opposite direction. So how can can add their length? It has to be be subtraction. If they are moving in the same direction then add only.
Kpkpkp said:
1 decade ago
When two trains move in opp direction you cant add length. Because length of smallest train is common to both. The actual distance travelled will be length of large train only.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers