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 7 of 25.
Vijay kumar kuppani said:
1 decade 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
Kalimuthu said:
1 decade 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
Prakash said:
1 decade 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
Nirmala said:
1 decade 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.
Sundaram said:
1 decade ago
Because train cross the bridge so we must add the length then only we will get the bridge length.
A.srinivas said:
1 decade ago
(x+130)/30=(45*5)/18
Mannu said:
1 decade ago
What is the significance of train's length. Since the train crossed the bridge so distance should be of the bridge only. Why that bridge and train added?
Janani said:
1 decade ago
How 5/18 came?plz xplain this..
Murali said:
1 decade ago
Hai! Janani while converting the distance it will come how means.
I) if you convert km/hr into m/sec then multiplies with "5/18".
Ii) if you convert m/sec into km/hr then multiplies with "18/5".
In this way, above problem the train speed is convert into the km/hr into m/sec. (because the answer is given in the form of meters).
Like this 5/18 will come.
I) if you convert km/hr into m/sec then multiplies with "5/18".
Ii) if you convert m/sec into km/hr then multiplies with "18/5".
In this way, above problem the train speed is convert into the km/hr into m/sec. (because the answer is given in the form of meters).
Like this 5/18 will come.
Murali said:
1 decade ago
@Mannu.
Here we know only length of the train. We have to find the length of the bridge. We know the formula"s=d/t".
Here distance is "L1+L2".
Therefore "s= (L1+L2) /t".
Now we will get the answer.
By adding two distance only we will find the one distance (if you know the one distance then find the length of the train).
Here we know only length of the train. We have to find the length of the bridge. We know the formula"s=d/t".
Here distance is "L1+L2".
Therefore "s= (L1+L2) /t".
Now we will get the answer.
By adding two distance only we will find the one distance (if you know the one distance then find the length of the train).
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