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 17 of 25.
Ayaz husain said:
1 decade ago
The role of 30 sec is, the first wheel of the train enters the bridge and the last wheel of the train leaves the other end point of the bridge in 30 sec. So the train has to train the bridge length plus the length of its own to cross the bridge.
Santosh said:
1 decade ago
Why we are subtracting the length of bridge?
K.vaishnavi said:
1 decade ago
Yes the simple method is:
Solution: Let length of the train = 130 m.
T = 30 s.
S = 45 km/hr.
= 45(5/18) m/s.
=12.5 m/s.
Distance = 12.5.
= 12.5*30 = 375.
Therefore the length of the bridge = 375-130 = 245 m.
Solution: Let length of the train = 130 m.
T = 30 s.
S = 45 km/hr.
= 45(5/18) m/s.
=12.5 m/s.
Distance = 12.5.
= 12.5*30 = 375.
Therefore the length of the bridge = 375-130 = 245 m.
Swamy said:
1 decade ago
Well,
36 sec --- 450 mt.
30 sec --- 375 mt.
Then, 375-135 = 275 mt.
36 sec --- 450 mt.
30 sec --- 375 mt.
Then, 375-135 = 275 mt.
Sharmin said:
1 decade ago
30 = 130+x/45*3.6 = 245.
Sonu said:
1 decade ago
Hi,
Could you please advise why we added x to the distance covered?
Could you please advise why we added x to the distance covered?
Reethu said:
1 decade ago
Hi,
Can anyone explain what is 5/18 here? I couldn't get this.
Can anyone explain what is 5/18 here? I couldn't get this.
Amar said:
1 decade ago
Train length bridge length train length.
Logically we should add train twice the train length, since crossing the bridge means train is not yet on the bridge and then it should be rolled off from bridge?
i.e , (x+2*130)/30 = 55 km/hr.
What say?
Logically we should add train twice the train length, since crossing the bridge means train is not yet on the bridge and then it should be rolled off from bridge?
i.e , (x+2*130)/30 = 55 km/hr.
What say?
Shekar v said:
1 decade ago
45000 meters/3600 seconds = 12.5.
12.5*30 sec = 375.
375-130 = 245.
12.5*30 sec = 375.
375-130 = 245.
Manmohan said:
1 decade ago
For a quick solution:
Let the length of the bridge be x.
Speed = 45*5/18 = 75/6 m/sec.
Time = 30 sec.
Length of train 130 m.
So we know Speed = Total distance/Time.
=> Total distance = Speed*Time.
=> x+130 = 75/6*30.
=> x= 245.
Hence the length of the bridge is 245 m.
Let the length of the bridge be x.
Speed = 45*5/18 = 75/6 m/sec.
Time = 30 sec.
Length of train 130 m.
So we know Speed = Total distance/Time.
=> Total distance = Speed*Time.
=> x+130 = 75/6*30.
=> x= 245.
Hence the length of the bridge is 245 m.
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