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:
245 comments Page 3 of 25.
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
@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).
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.
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......
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