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:
249 comments Page 12 of 25.
Sushi said:
1 decade ago
HEY. I have a doubt. The length of train is already covering some length of the bridge. Then why we consider both lengths separately?
Mano said:
1 decade ago
Your are right sushi.
Please help why we consider both lengths separately?
If the train is crossed 130m length in 10 sec it also covered length of bridge?
Why we are again consider the bridge length?
The train is already crossed the bridge in 10 sec. So the length of the bridge also covered.
Please help why we consider both lengths separately?
If the train is crossed 130m length in 10 sec it also covered length of bridge?
Why we are again consider the bridge length?
The train is already crossed the bridge in 10 sec. So the length of the bridge also covered.
Shoeb said:
1 decade ago
Formula :- Distance=Speed/Time
Answer's in option are given in meter, that mean we can go for 5/18 ready made formula of converting km/hr to m/sec.
* 45 x 5/18 = 12.5 (for 1 second )
* 12.5(sec) x 30(sec)given = 375
* 375-130 (given )= 245.
Answer's in option are given in meter, that mean we can go for 5/18 ready made formula of converting km/hr to m/sec.
* 45 x 5/18 = 12.5 (for 1 second )
* 12.5(sec) x 30(sec)given = 375
* 375-130 (given )= 245.
Parthiban said:
1 decade ago
Easy to find no need to put x and y.
45000m/360seconds = 125 mps.
30 seconds so, crossing bridge.
30*125=375m.
Subtract the train meter : 130m.
Answer : 375-130=245m.
45000m/360seconds = 125 mps.
30 seconds so, crossing bridge.
30*125=375m.
Subtract the train meter : 130m.
Answer : 375-130=245m.
Srikant kumar said:
1 decade ago
Best Answer could be for new person:
3600 sec me 45000 meter.
1 sec me 45000/3600 12.5 meter/sec.
30 sec me 12.5*30 = 375 meter.
Train length is 130 meter .
Bridge length will be :-375-130 = 245 meter.
3600 sec me 45000 meter.
1 sec me 45000/3600 12.5 meter/sec.
30 sec me 12.5*30 = 375 meter.
Train length is 130 meter .
Bridge length will be :-375-130 = 245 meter.
Monika said:
1 decade ago
You can do this without any variable:
45 km/hr*5/18 = 25/2 m/s.
Total distance = 25/2*30 = 375.
Length of bridge = 375-130 = 245m.
45 km/hr*5/18 = 25/2 m/s.
Total distance = 25/2*30 = 375.
Length of bridge = 375-130 = 245m.
Rohit said:
1 decade ago
Please help me,
When the train crosses the bridge, shouldn't we consider the length of the train after the bridge also.
All above solutions are only by considering the start point of the train.
And if only that is considered then what is the use of the length of the train.
When the train crosses the bridge, shouldn't we consider the length of the train after the bridge also.
All above solutions are only by considering the start point of the train.
And if only that is considered then what is the use of the length of the train.
Ananth G said:
1 decade ago
@Rohit,
Length=(speed*time).
What you know take left side others stay right side, listen down.
Length
------- = speed {(130+X)/30=25/2,
Time
Than you workout cross multiply method then you get 245m.
Length=(speed*time).
What you know take left side others stay right side, listen down.
Length
------- = speed {(130+X)/30=25/2,
Time
Than you workout cross multiply method then you get 245m.
Dileep kumar said:
1 decade ago
Distance = speed/time;
Let us bridge length = x say, train travelling distance = 130 m.
The total distance is = x+130;
Speed = 25/2;time = 30sec;
:: x+130 = (25/2) 30;
x = 375-130;
= 245.
Let us bridge length = x say, train travelling distance = 130 m.
The total distance is = x+130;
Speed = 25/2;time = 30sec;
:: x+130 = (25/2) 30;
x = 375-130;
= 245.
Sunil Kumar said:
1 decade ago
Let bridge length x m then.
Length of train = 130.
Speed 45*5/18 = 12.5.
Distance=12.5*30 = 375.0-130 = 245.
Length of train = 130.
Speed 45*5/18 = 12.5.
Distance=12.5*30 = 375.0-130 = 245.
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