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 24 of 26.
Sundaram said:
2 decades ago
Because train cross the bridge so we must add the length then only we will get the bridge length.
Nirmala said:
2 decades ago
Why train length added with bridge length what's the logic behind it?
Why bridge length is not subtracted from train length?
Please clear my doubt.
Why bridge length is not subtracted from train length?
Please clear my doubt.
Prakash said:
2 decades ago
speed=[45*(5/18)]=25/2 m/hr
time=30 sec
s=d/t
distance= speed*time
(25/2)* 30=375
375-130= 245
is this ryt
time=30 sec
s=d/t
distance= speed*time
(25/2)* 30=375
375-130= 245
is this ryt
Kalimuthu said:
2 decades ago
A train cross 1 hour =45km
so that Trian cross in 1 hour =45000m(1km=1000m)
so that trian cross in3600seconds=45000m(1hour=3600sec)
so that trian cross in one second is 45000/3600=12.5m
now 30 sec cross the bridge 12.5*30=375
so that trian length is 130m
so we proof 375-130=245METERS
so that Trian cross in 1 hour =45000m(1km=1000m)
so that trian cross in3600seconds=45000m(1hour=3600sec)
so that trian cross in one second is 45000/3600=12.5m
now 30 sec cross the bridge 12.5*30=375
so that trian length is 130m
so we proof 375-130=245METERS
Vijay kumar kuppani said:
2 decades ago
THE SIMPLEST WAY OF SOLVING THIS PROBLEM
train speed=45km/hr=>45*(5/18)=25/2 m/sec;
25/2 m/sec means
the train can travel a distance of 25/2 meters in 1 sec
1 sec--->25/2mts
30sec--->(25/2)*30=>375meters
therefore the total distance covered by the train in 30 seconds is 375 meters(i,e train length+bridge length)
by subtracting the train length from the total distance we can find out the length of the bridge i,e
375-130=245 meters
train speed=45km/hr=>45*(5/18)=25/2 m/sec;
25/2 m/sec means
the train can travel a distance of 25/2 meters in 1 sec
1 sec--->25/2mts
30sec--->(25/2)*30=>375meters
therefore the total distance covered by the train in 30 seconds is 375 meters(i,e train length+bridge length)
by subtracting the train length from the total distance we can find out the length of the bridge i,e
375-130=245 meters
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????????
Sunny said:
2 decades ago
Hey boopathi its simple.
2(130+x)=750
130+x=750/2
130+x=375
x=375-130
Therefore x = 245.
2(130+x)=750
130+x=750/2
130+x=375
x=375-130
Therefore x = 245.
Mubeen said:
2 decades ago
@Coolburn
Yep... Quite simple and understandable.
Yep... Quite simple and understandable.
Gkvinodh said:
2 decades ago
How the equation (130 + x) /2 = 25/2 comes ?
Coolburn said:
2 decades ago
Hi, I had my own solustion on that
45 km/hr
1km = 1000m
1hr = 3600 sec
45 km/hr convert to metter
=45000 m
=3600 sec.
45000/3600
=12.5
Since 30 sec can cross the bridge
=12.5*30
=375-130
=245m
45 km/hr
1km = 1000m
1hr = 3600 sec
45 km/hr convert to metter
=45000 m
=3600 sec.
45000/3600
=12.5
Since 30 sec can cross the bridge
=12.5*30
=375-130
=245m
(1)
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