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 1 of 4.
Sandeep said:
1 decade ago
(120 + 120) from where it comes?
Dinesh said:
1 decade ago
How 18/5 came?
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.
Vaibhav Singh said:
1 decade ago
If we are talking about relative distance then it should be only 120m.
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.
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'.
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
Why we have to take 60*60 and why we have to convert 120 to km not km/hr?
Nisha said:
1 decade ago
In the previous question we are taking the length of the single train, but in this question we are using both the length. Please clarify?
Justin said:
1 decade ago
Here speed and distance where same so we just need to calculate.
s = d/t which means x = 120/12 = 10 then convert it into Km using 10*18/5 = 36.
s = d/t which means x = 120/12 = 10 then convert it into Km using 10*18/5 = 36.
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