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 6 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.
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.
(13)
Ani said:
7 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:
1 decade 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......
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....
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers