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 5 of 7.
Jagadheesh said:
1 decade ago
How to find that this problem is need to convert km/hr to m/s or m/s to km/hr. Please explain?
Maneesh said:
1 decade ago
Can anyone please tell me when to add or subtract the given relative speeds.
Ronit said:
1 decade ago
Easy way.
270 + x
---------------- = 9.
33.33+22.22
x = 499.5 - 270.
x = 229.5.
270 + x
---------------- = 9.
33.33+22.22
x = 499.5 - 270.
x = 229.5.
Mancy said:
1 decade ago
@Janani.
The concept of relative speed is still the basic time, speed and distance formula applied to distance between two moving bodies.
In a simple case of the distance.
Formula, a body traveling with a speed of 50 km/h is reducing the gap between its starting point and the finish point by 50 km every hour.
&
In the relative speed case of the distance formula two moving bodies, traveling at a relative speed of 50 km/h towards/away from each other, are reducing/increasing the gap between them by 50 km every hour.
Hope this help.
The concept of relative speed is still the basic time, speed and distance formula applied to distance between two moving bodies.
In a simple case of the distance.
Formula, a body traveling with a speed of 50 km/h is reducing the gap between its starting point and the finish point by 50 km every hour.
&
In the relative speed case of the distance formula two moving bodies, traveling at a relative speed of 50 km/h towards/away from each other, are reducing/increasing the gap between them by 50 km every hour.
Hope this help.
Janani said:
1 decade ago
I want to know one thing usually where we use or apply this relative speed concept ?
Abhishek Pandey said:
1 decade ago
Always opposite will add and same will be subtract.
Moni said:
1 decade ago
Relative speed should be minus from each train speed because the direction is opposite, isn't it so?
Santosh adithya said:
1 decade ago
Why there is (x+270)/9 acc. to formula (270+x)/500/9 = 9 right?
Kd kannan said:
1 decade ago
To aswin:
100/3 and 120 (5/18).
Two values are equal.
It is another form of 33.3.
100/3 and 120 (5/18).
Two values are equal.
It is another form of 33.3.
Sabira said:
1 decade ago
Speed = 120+80 = 200 km/hr.
200* (5/18) = 500/9m/sec.
Total length = 500/9*9.
= 500 m.
500 - 270 = 230 is the other train length.
200* (5/18) = 500/9m/sec.
Total length = 500/9*9.
= 500 m.
500 - 270 = 230 is the other train length.
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