Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 9)
9.
Two trains are moving in opposite directions @ 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is:
Answer: Option
Explanation:
Relative speed = (60+ 90) km/hr
| = |  |
150 x | 5 |  m/sec |
| 18 |
| = | |
125 | m/sec. |
| 3 |
Distance covered = (1.10 + 0.9) km = 2 km = 2000 m.
| Required time = | |
2000 x | 3 | sec = 48 sec. |
| 125 |
Discussion:
107 comments Page 8 of 11.
Aasif Khan said:
1 decade ago
This is due, when we calculate time= distance/speed,
Speed is 125/3 m/sec. Therefore when we divide 2000m with 125/3 it becomes 2000 multiply by 3/125.
Speed is 125/3 m/sec. Therefore when we divide 2000m with 125/3 it becomes 2000 multiply by 3/125.
Divyan said:
1 decade ago
Why we are not simplifying 125/3? Please help me guys.
Avinash Upadhyay said:
1 decade ago
@Divyan, here we are converting the speed into meter/sec from km/hr .
(1km = 1000m
1hr = 3600sec
m/sec = 1000/3600 = 5/18.)
150*25/3 = 125/3.
And relative speed comes into picture when two given objects in the questions are in motion.
(1km = 1000m
1hr = 3600sec
m/sec = 1000/3600 = 5/18.)
150*25/3 = 125/3.
And relative speed comes into picture when two given objects in the questions are in motion.
Ajit vishwakarma said:
1 decade ago
What do you mine time taken by the slower train to cross the faster train?
ParthShah said:
1 decade ago
Point 1: Trains are running in opposite directions so the slower train will cross the faster one.
Point 2: The time taken by slower train to cross faster train would be equal to the vice versa.
Point 2: The time taken by slower train to cross faster train would be equal to the vice versa.
Anand said:
1 decade ago
Why 5/18?
Amrutha said:
1 decade ago
In the above given that:
T = x+y/u+v for opposite direction.
Can you please apply in this problem?
T = x+y/u+v for opposite direction.
Can you please apply in this problem?
Agasthya Rana said:
1 decade ago
Why are we adding speed?
Sateesh Vudum said:
1 decade ago
For every problem like this you should find relative speed to get solution.
Need of relative speed: we can desire the solution without forming the relation between two quantities either speed or time.
Time = (L1+L2)/(relative speed);
L1-Length of train-1.
L2-Length of train-2.
Need of relative speed: we can desire the solution without forming the relation between two quantities either speed or time.
Time = (L1+L2)/(relative speed);
L1-Length of train-1.
L2-Length of train-2.
Riyaz said:
1 decade ago
Hi friends. I have one doubt when the trains are moving in opposite direction we add the speed of those trains but why we have to add the length of the two trains. Please explain me.
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