Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 13)
13.
Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. If one is moving twice as fast the other, then the speed of the faster train is:
Answer: Option
Explanation:
Let the speed of the slower train be x m/sec.
Then, speed of the faster train = 2x m/sec.
Relative speed = (x + 2x) m/sec = 3x m/sec.
 |
(100 + 100) | = 3x |
| 8 |
24x = 200
| x = |
25 | . |
| 3 |
| So, speed of the faster train = | 50 | m/sec |
| 3 |
| = |  |
50 | x | 18 |  km/hr |
| 3 | 5 |
= 60 km/hr.
Discussion:
74 comments Page 3 of 8.
Jai said:
9 years ago
If 1st train accelerated by 0.3 and 2nd 0.2 then how to solve it?
Sam said:
9 years ago
@Aditiyabala.
Super explanation, Thank you.
Super explanation, Thank you.
Praveen Sharma said:
10 years ago
How come 3?
Answer - If speed of slow train is x km/h.
In question the speed of fast train is twice to slow train.
So speed of fast train = 2*(Speed of slow train).
So speed of fast train = 2*(x) = 2x.
If trains are moving in opposite direction then we ADD the Speed. And trains are in same direction then we sub speed.
Here train in same direction so we add the speed of both train.
So x + 2x = 3x.
Answer - If speed of slow train is x km/h.
In question the speed of fast train is twice to slow train.
So speed of fast train = 2*(Speed of slow train).
So speed of fast train = 2*(x) = 2x.
If trains are moving in opposite direction then we ADD the Speed. And trains are in same direction then we sub speed.
Here train in same direction so we add the speed of both train.
So x + 2x = 3x.
Srinu said:
10 years ago
What is formula distance?
Shiva said:
1 decade ago
Why you are all talking always 5/18 to convert kmph into m/sec, I can't understand that logic, please explain reason behind that. Thanks in advance.
K.ratnababu said:
8 years ago
This is another way.
two trains opposite direction 100m+100m=200m.
200m to cover 8 seconds then,
(200m 8sec
? 3600sec
90000m that means 90k).
3600sec that mean 1 hour to cover 90000m that is 90k/h.
the train speed is 2:1.
total 3 parts.
3parts 90kilometers then,
2parts ?
60k.
two trains opposite direction 100m+100m=200m.
200m to cover 8 seconds then,
(200m 8sec
? 3600sec
90000m that means 90k).
3600sec that mean 1 hour to cover 90000m that is 90k/h.
the train speed is 2:1.
total 3 parts.
3parts 90kilometers then,
2parts ?
60k.
Garvit said:
8 years ago
Why wasn't the speed of one train 1 considered x and other considered y? Why we're both taken as x?
Eudis said:
7 years ago
From where did 18/5 come? Please explain me.
Ganesh said:
7 years ago
Consider one train x speed and another one is x one twice speed to the other train then x+2x-3x.
Reeha said:
7 years ago
@Eudis.
It's the basic conversion principle, From km/hr to m/s we can use 5/18 and the reciprocal for vice versa.
It's the basic conversion principle, From km/hr to m/s we can use 5/18 and the reciprocal for vice versa.
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