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:
254 comments Page 7 of 26.
Sssss said:
1 decade ago
Simple method:
Speed = 45 x 5/18 m/sec = 25/2 m/sec.
Time = 30 sec.
Let the length of bridge be x metres.
Then, 130 + x /30 = 25/2.
2(130 + x) = 30*25.
2(130 + x) = 750.
260+2x = 750.
2x = 750-260.
2x = 490.
x = 490/2.
x = 245.
Speed = 45 x 5/18 m/sec = 25/2 m/sec.
Time = 30 sec.
Let the length of bridge be x metres.
Then, 130 + x /30 = 25/2.
2(130 + x) = 30*25.
2(130 + x) = 750.
260+2x = 750.
2x = 750-260.
2x = 490.
x = 490/2.
x = 245.
Vinu said:
1 decade ago
I've a doubt, if the bridge length is greater than the length of the train, then the train need to travel twice it's length + (bridge length-train length) to cross the bridge, why that factor is not considering in this problem?
Shahul hameed.M said:
1 decade ago
Am telling the easy way to solve this problem......
in basic formula is
L=speed*time
here we wanna 2 find length of the bridge so,
L1+L2=speed *time(L1=length of the train,L2=length of the bridge)v can get d ans easily....
in basic formula is
L=speed*time
here we wanna 2 find length of the bridge so,
L1+L2=speed *time(L1=length of the train,L2=length of the bridge)v can get d ans easily....
Sandeep said:
1 decade ago
It is easy,
Train length = 130mtr,
Speed = 45km/hr,
Time = 30sec.
First:-
Converting the speed:- 45*5/18 = 12.5,
Then, total distance = speed * time.
= 12.5 * 30 = 375.
Therefore, the length of bridge = 375 - 130 = 245.
Train length = 130mtr,
Speed = 45km/hr,
Time = 30sec.
First:-
Converting the speed:- 45*5/18 = 12.5,
Then, total distance = speed * time.
= 12.5 * 30 = 375.
Therefore, the length of bridge = 375 - 130 = 245.
Ruby said:
2 decades ago
Hey frnd........i sol dis prob in diff way..
length of train=130m
speed=45km/hr
time=30sec
l=s*t
l=(45*5/18)*30
l=(25/2)*30
l=375
length of bridge=l-length of train
x=375-130
x=245m...........
is dis is rite method????????
length of train=130m
speed=45km/hr
time=30sec
l=s*t
l=(45*5/18)*30
l=(25/2)*30
l=375
length of bridge=l-length of train
x=375-130
x=245m...........
is dis is rite method????????
Sara said:
1 decade ago
Total distance of bridge is 45Km/hr*(30/360)hrs =45/12Kms
Distance in metres = (45/12)*100 =375 Metres
Distance covered = 375M -130M =245M
I believe this is the quickest way given the time allocated in such assessments.
Distance in metres = (45/12)*100 =375 Metres
Distance covered = 375M -130M =245M
I believe this is the quickest way given the time allocated in such assessments.
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.
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.
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.
Subramanyam subbu said:
1 decade ago
distance=speed*time
assume length of bridge as x meters
here distance=(length of bridge+length of train)
x+130=45*(5/18)
[ 5/18 indictes conversion of km/hr to m/sec)
we get x= 245 m i.e length of the bridge
assume length of bridge as x meters
here distance=(length of bridge+length of train)
x+130=45*(5/18)
[ 5/18 indictes conversion of km/hr to m/sec)
we get x= 245 m i.e length of the bridge
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