Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 3)
3.
The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:
Answer: Option
Explanation:
| Speed = |  |
45 x | 5 |  m/sec |
= | |
25 | m/sec. |
| 18 | 2 |
Time = 30 sec.
Let the length of bridge be x metres.
| Then, | 130 + x | = | 25 |
| 30 | 2 |
2(130 + x) = 750
x = 245 m.
Video Explanation: https://youtu.be/M_d8WufJWKc
Discussion:
250 comments Page 8 of 25.
Sundaram said:
2 decades ago
Because train cross the bridge so we must add the length then only we will get the bridge length.
A.srinivas said:
2 decades ago
(x+130)/30=(45*5)/18
Mannu said:
2 decades ago
What is the significance of train's length. Since the train crossed the bridge so distance should be of the bridge only. Why that bridge and train added?
Janani said:
2 decades ago
How 5/18 came?plz xplain this..
Murali said:
2 decades ago
Hai! Janani while converting the distance it will come how means.
I) if you convert km/hr into m/sec then multiplies with "5/18".
Ii) if you convert m/sec into km/hr then multiplies with "18/5".
In this way, above problem the train speed is convert into the km/hr into m/sec. (because the answer is given in the form of meters).
Like this 5/18 will come.
I) if you convert km/hr into m/sec then multiplies with "5/18".
Ii) if you convert m/sec into km/hr then multiplies with "18/5".
In this way, above problem the train speed is convert into the km/hr into m/sec. (because the answer is given in the form of meters).
Like this 5/18 will come.
Murali said:
2 decades ago
@Mannu.
Here we know only length of the train. We have to find the length of the bridge. We know the formula"s=d/t".
Here distance is "L1+L2".
Therefore "s= (L1+L2) /t".
Now we will get the answer.
By adding two distance only we will find the one distance (if you know the one distance then find the length of the train).
Here we know only length of the train. We have to find the length of the bridge. We know the formula"s=d/t".
Here distance is "L1+L2".
Therefore "s= (L1+L2) /t".
Now we will get the answer.
By adding two distance only we will find the one distance (if you know the one distance then find the length of the train).
Periyasamy v said:
2 decades ago
I solved my own speed of the train 45km/hr,then change into 45000m/hr,then chang into per second (45000/3600)=12.5 m/sec,then multiple with 30sec,(12.5*30)=375, then mins the train length 375-130=245 i think this s correct......
RAEES said:
2 decades ago
Nusrath fathima solved method is better.
Chithu said:
2 decades ago
Very useful methods.
Rajan said:
2 decades ago
Periyasamy is perfectly correct and is the correct logic to solve the problem.
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