Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 24)
24.
Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction?
Answer: Option
Explanation:
| Speed of the first train = |  |
120 |  |
m/sec = 12 m/sec. |
| 10 |
| Speed of the second train = | |
120 | |
m/sec = 8 m/sec. |
| 15 |
Relative speed = (12 + 8) = 20 m/sec.
 Required time = |
 |
(120 + 120) | ![]](/_files/images/aptitude/1-sym-cbracket-h1.gif) |
sec = 12 sec. |
| 20 |
Discussion:
22 comments Page 1 of 3.
AUNRAJ JAGTAP said:
7 months ago
Very nice, Thanks for explaining the answer.
Nikhil said:
5 years ago
Speed of T1 = 120/10 = 12m/s.
Speed of T2 = 120/15 = 8m/s.
Time taken to cross each other = D/S = (120 + 120)/12 + 8 = 12 secs.
Speed of T2 = 120/15 = 8m/s.
Time taken to cross each other = D/S = (120 + 120)/12 + 8 = 12 secs.
(3)
Shweta said:
6 years ago
Why didn't we take (15+10) directly as speed like we add in other questions.
(1)
Srijan das said:
6 years ago
The answer should be 6.
And 120m should be the length considered for the opposite direction.
When travelling in same direction, the length should be 120+120.
And 120m should be the length considered for the opposite direction.
When travelling in same direction, the length should be 120+120.
(1)
Sam said:
6 years ago
This problem should tell us,two trains are coming from opposite sid.
(1)
Shree said:
7 years ago
Thank you all for explaining the answer.
Priya said:
8 years ago
Why are we not calculate this way,
s = 120+120/10+15,
= 9.6 m/s.
Correct me if I am wrong.
s = 120+120/10+15,
= 9.6 m/s.
Correct me if I am wrong.
(1)
Akhilesh said:
9 years ago
Anyone can explain this problem? because I'm not understand this problem.
Vinayak PB said:
9 years ago
It's simple, just add both train durations i.e. 10s + 15s = 25s.
And just check mid point ie 25/2.
We get 12.5 so literally equal to 12s.
And just check mid point ie 25/2.
We get 12.5 so literally equal to 12s.
Harishankar said:
9 years ago
We will add 120 + 120 because of two different speeds of trains. If both trains having equal length and equal speed its not necessary to add lengths.
(2)
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