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:
247 comments Page 19 of 25.
Sathiyaraj said:
9 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:
9 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.
Sandhya said:
9 years ago
Can you explain me in detail? I can't understand.
Vinod choudhary said:
9 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.
TFreeN said:
9 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:
9 years ago
Why 18/5?
Sathiyaraj said:
9 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.
Peter said:
9 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.
Anusha said:
9 years ago
Here, the formula is:
Time is taken to cross the bridge = length of the bridge + length of the train/speed of the train.
To convert km to m we have to multiply with = (5/18).
Converting km to m:
45 * 5/18 = 25/2.
Assume length of the bridge be x then,
30 = (x + 130)/(25/2),
So by calculating we get the x value i.e length of the bridge.
Time is taken to cross the bridge = length of the bridge + length of the train/speed of the train.
To convert km to m we have to multiply with = (5/18).
Converting km to m:
45 * 5/18 = 25/2.
Assume length of the bridge be x then,
30 = (x + 130)/(25/2),
So by calculating we get the x value i.e length of the bridge.
Vaishak said:
9 years ago
I am just bewildered why they have added the train length with bridge length and why not just the bridge length because it is the actual distance the train has to pass through isn't it?Anybody please answer me.
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