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 6 of 26.
Draco said:
6 months ago
So the train must go faster than the man to pass him.
S = D/T.
Meters to km = 18/5,
s = d/t,
d = 125 x 18/5 = 450.
t = 10.
s = 450/10 = 45.
The speed we calculate (45 km/hr) is the extra speed the train has compared to the man.
45 + 5 = 50km/hr.
S = D/T.
Meters to km = 18/5,
s = d/t,
d = 125 x 18/5 = 450.
t = 10.
s = 450/10 = 45.
The speed we calculate (45 km/hr) is the extra speed the train has compared to the man.
45 + 5 = 50km/hr.
(4)
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?
Fearless said:
1 year ago
The speed of train in sec = 45000/3600 = 12.5sec.
distance travel by train in 30 sec = 12.5 * 30 = 375m,
lenght of train = 130m.
Length of bridge = distance traveled by the train - length of train.
= 375-130 = 245m.
distance travel by train in 30 sec = 12.5 * 30 = 375m,
lenght of train = 130m.
Length of bridge = distance traveled by the train - length of train.
= 375-130 = 245m.
(63)
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.
Shoeb said:
1 decade ago
Formula :- Distance=Speed/Time
Answer's in option are given in meter, that mean we can go for 5/18 ready made formula of converting km/hr to m/sec.
* 45 x 5/18 = 12.5 (for 1 second )
* 12.5(sec) x 30(sec)given = 375
* 375-130 (given )= 245.
Answer's in option are given in meter, that mean we can go for 5/18 ready made formula of converting km/hr to m/sec.
* 45 x 5/18 = 12.5 (for 1 second )
* 12.5(sec) x 30(sec)given = 375
* 375-130 (given )= 245.
Lovepreet kaur said:
1 decade ago
I have solved this problem in another way.
Here am explaining it.
Distance=speed*time;
Length of train = 130m.
Speed = 45 km/hr or 45*1000/3600 m/sec.
Time = 30 sec.
Length = (45*1000/3600)*30 = 375m.
Length of bridge = 375-130 = 245m.
Here am explaining it.
Distance=speed*time;
Length of train = 130m.
Speed = 45 km/hr or 45*1000/3600 m/sec.
Time = 30 sec.
Length = (45*1000/3600)*30 = 375m.
Length of bridge = 375-130 = 245m.
Adesh Katiya said:
2 years ago
l = ?
Train length =130m
Speed = 45km/hr
Time = 30s.
30s = time(130+l(m)).
30s = (130+l)m/45km/hr.
30s = (130+l)m/45 * 5/18m/s.
30s = 130+l/(25/2)m/s.
30s = (130+l) * 2/25.
30 * 25 = (130 +l)* 2.
15*25 = 130 + l.
375 - 130 = l.
245m = l.
Train length =130m
Speed = 45km/hr
Time = 30s.
30s = time(130+l(m)).
30s = (130+l)m/45km/hr.
30s = (130+l)m/45 * 5/18m/s.
30s = 130+l/(25/2)m/s.
30s = (130+l) * 2/25.
30 * 25 = (130 +l)* 2.
15*25 = 130 + l.
375 - 130 = l.
245m = l.
(14)
Ani said:
8 years ago
@Sarang you are correct this is the easiest way to solve this problem.
As
Distance= time * speed.
D=45*5/18=25/2(speed)*30(time),
Actual distance=25 * 15=375.
Then bridge distance=Actual distance (375)- train Distance (130)=245.
As
Distance= time * speed.
D=45*5/18=25/2(speed)*30(time),
Actual distance=25 * 15=375.
Then bridge distance=Actual distance (375)- train Distance (130)=245.
BaluRajasekaran said:
1 decade ago
45 km/hr = 12.5 m/s
then the train travel 375 m in 30 seconds
[i.e] 12.5[speed] * 30[total time to reach] = 375[this is the time the train completely out of the bridge]
then the length of bridge is 375 - 130[length of train]= 245
then the train travel 375 m in 30 seconds
[i.e] 12.5[speed] * 30[total time to reach] = 375[this is the time the train completely out of the bridge]
then the length of bridge is 375 - 130[length of train]= 245
Periyasamy v said:
2 decades ago
I solved my own speed of the train 45km/hr,then change into 45000m/hr,then chang into per second (45000/3600)=12.5 m/sec,then multiple with 30sec,(12.5*30)=375, then mins the train length 375-130=245 i think this s correct......
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