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 16 of 25.
Pradnya said:
1 decade ago
I can't understand your answer please explain.
Jitendra said:
1 decade ago
Can we try this way?
Length of train + Length of bridge = (Distance which train need to be cover in 30 sec).
(130 m + X)---(1)-X = Suppose length of bridge.
Speed of trains = 45 km/h speed given in km/h hence convert it in m/sec.
45*5/18 = 25/2 ----- (2).
From equation (1) and (2).
= 25/2 = (130+X)/30.
= 25*30 = 260+2X.
= 750-260 = 2X.
= 490/2 = X.
= 245 = X.
Hence length of bridge (X) will be 245 m.
Length of train + Length of bridge = (Distance which train need to be cover in 30 sec).
(130 m + X)---(1)-X = Suppose length of bridge.
Speed of trains = 45 km/h speed given in km/h hence convert it in m/sec.
45*5/18 = 25/2 ----- (2).
From equation (1) and (2).
= 25/2 = (130+X)/30.
= 25*30 = 260+2X.
= 750-260 = 2X.
= 490/2 = X.
= 245 = X.
Hence length of bridge (X) will be 245 m.
Dinesh said:
1 decade ago
As the train crosses, which means the train should start at the starting of bridge and completely leave the bridge.
So, (130+x+130) should be the distance traveled in 30 secs.
= (130+x+130)/30 = (45*5/18).
x = 115.
So, (130+x+130) should be the distance traveled in 30 secs.
= (130+x+130)/30 = (45*5/18).
x = 115.
Poonam Pipaliya said:
1 decade ago
What is role of 30 sec and from where it comes?
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:
10 years 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:
10 years ago
30 = 130+x/45*3.6 = 245.
Sonu said:
10 years 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?
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