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:
252 comments Page 11 of 26.
Peter said:
10 years ago
I think it would be better if we say the train is running by 45 KM/HR so let's take it in details KM/HR = 1000 M/3600 S so = 10 /36 = 5 /18.
So, train is running by 45 KM/HR = 45 * (5/18) = 12.5 M/S.
Crossed bridge in 30 S so 12.5 * 30 = 375 minus it's from train length so 375 - 130 = 245 M the length of the bridge.
Wish to be easier.
So, train is running by 45 KM/HR = 45 * (5/18) = 12.5 M/S.
Crossed bridge in 30 S so 12.5 * 30 = 375 minus it's from train length so 375 - 130 = 245 M the length of the bridge.
Wish to be easier.
Sathiyaraj said:
10 years ago
@Kavya &@Sandhya.
The entire train coaches should pass the bridge.
Here we don't know the length of the bridge, so let be x.
Train length is 130 m.
So, the distance covered by train is , 350 + x mts.
The entire train coaches should pass the bridge.
Here we don't know the length of the bridge, so let be x.
Train length is 130 m.
So, the distance covered by train is , 350 + x mts.
TFreeN said:
10 years ago
This is very shortcut key.
Simple 45km = 45000 mitr.
1hrs = 3600 sec.
= 45000/3600.
=12.5.
12.5 * 30 second cross.
= 375.
And 375 - 130 mtr.
= 245 mtr.
Simple 45km = 45000 mitr.
1hrs = 3600 sec.
= 45000/3600.
=12.5.
12.5 * 30 second cross.
= 375.
And 375 - 130 mtr.
= 245 mtr.
Premasing s rathod said:
10 years ago
Why 18/5?
Vinod choudhary said:
10 years ago
Speed = (length of bridge + length of train) /time = (L + l) /t.
45 x (5/18) = (L + 130) /30,
45 x 30 x (5/18) = (L + 130) ,
375 = L + 130,
L = 375 - 130,
L = 245 m.
45 x (5/18) = (L + 130) /30,
45 x 30 x (5/18) = (L + 130) ,
375 = L + 130,
L = 375 - 130,
L = 245 m.
Sandhya said:
10 years ago
Can you explain me in detail? I can't understand.
Kavya said:
10 years ago
Why are you using '130 + x' ?
Sathiyaraj said:
10 years ago
45 km/hr => 45, 000 mts = 3600 sec=>36 s = 450 mts.
Let x be the bridge length.
In 30 sec, trains crosses, 130m + x = 30 sec,
=> (36/6) *5 sec = (450/6) *5 mts,
So, 30 sec = 375 mts,
So, x = 375-130 => x = 245 mts.
Let x be the bridge length.
In 30 sec, trains crosses, 130m + x = 30 sec,
=> (36/6) *5 sec = (450/6) *5 mts,
So, 30 sec = 375 mts,
So, x = 375-130 => x = 245 mts.
Santosh said:
10 years ago
No, WRONG ANSWER.
The correct answer is 115M.
X + 0.260km = 45 * 30/(60 * 60),
X + 0.26 = 0.375,
=> X= 0.115 KM = 115METERS.
The correct answer is 115M.
X + 0.260km = 45 * 30/(60 * 60),
X + 0.26 = 0.375,
=> X= 0.115 KM = 115METERS.
Janani said:
10 years ago
How get 5/18?
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