Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 23)
23.
Two trains are running in opposite directions with the same speed. If the length of each train is 120 metres and they cross each other in 12 seconds, then the speed of each train (in km/hr) is:
Answer: Option
Explanation:
Let the speed of each train be x m/sec.
Then, relative speed of the two trains = 2x m/sec.
| So, 2x = | (120 + 120) |
| 12 |
2x = 20
x = 10.
 Speed of each train = 10 m/sec = |
 |
10 x | 18 |  |
km/hr = 36 km/hr. |
| 5 |
Discussion:
38 comments Page 4 of 4.
Divya said:
1 decade ago
Why we have to take 60*60 and why we have to convert 120 to km not km/hr?
Divya said:
1 decade ago
@Chandana said that if trains are moving in opposite direction we have to take only one train length. But in 23 question we are taking both train speeds? please clarify.
Divya said:
1 decade ago
In different situations we are taking relative speed? in which situations we have to find relative speed? and in which situations we have to assume 'x'.
Sasikala S said:
1 decade ago
There is an easier way.
Speed = distance/time.
Here, distance = 120 m i.e., 0.12 km; time = 12 sec i.e., 12/60 x 60 hrs.
Hence, speed = 0.12/ (12/3600) = (0.12*3600) /12 = 36 km/hr.
Speed = distance/time.
Here, distance = 120 m i.e., 0.12 km; time = 12 sec i.e., 12/60 x 60 hrs.
Hence, speed = 0.12/ (12/3600) = (0.12*3600) /12 = 36 km/hr.
Vaibhav Singh said:
1 decade ago
If we are talking about relative distance then it should be only 120m.
Santhosh said:
1 decade ago
It is the length of two trains i.e., (120+120)
and 18/5 is conversion of m/s to km/hr.
and 18/5 is conversion of m/s to km/hr.
Dinesh said:
1 decade ago
How 18/5 came?
Sandeep said:
1 decade ago
(120 + 120) from where it comes?
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