Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 8)
8.
A train 360 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 140 m long?
Answer: Option
Explanation:
| Formula for converting from km/hr to m/s: X km/hr = |  |
X x | 5 |  |
m/s. |
| 18 |
| Therefore, Speed = | |
45 x | 5 | m/sec |
= | 25 | m/sec. |
| 18 | 2 |
Total distance to be covered = (360 + 140) m = 500 m.
| Formula for finding Time = | |
Distance | |
| Speed |
 Required time = |
|
500 x 2 | sec |
= 40 sec. |
| 25 |
Discussion:
78 comments Page 1 of 8.
Satish said:
1 decade ago
When a train is crossing a bridge means that train is crossing it's own length and the bridge length. If you see at the end of the compartment to be crossed the bridge, the length of the bridge is depending on the train length, if the train is shorter the the time taken to cross the bridge will be lesser and if the train is longer, the time taken to bridge will be larger to cross at the end of the compartment.
Saud said:
1 decade ago
Length Of the train = 360m.
Speed of train = 45km/hr.
Converting it into m/s = 45*1000/3600.
= 45*5/18 (after basic cancellation).
= 25/2 m/s.
Now, let time required by train to cover 140m long bridge = x sec.
Therefore, t = d/s.
x= (train length + platform length) /speed of train.
Therefore, x= (360+140) / 25/2.
x = 500*2/25.
x = 40 sec.
Easiest some until now. Thank You. Hope it helped you.
Speed of train = 45km/hr.
Converting it into m/s = 45*1000/3600.
= 45*5/18 (after basic cancellation).
= 25/2 m/s.
Now, let time required by train to cover 140m long bridge = x sec.
Therefore, t = d/s.
x= (train length + platform length) /speed of train.
Therefore, x= (360+140) / 25/2.
x = 500*2/25.
x = 40 sec.
Easiest some until now. Thank You. Hope it helped you.
Rohit yadav said:
1 decade ago
If the units are in km/hr .
for example speed= 10km/hr
and time = 5 sec.
Then to find distance in meters..... How will you calculate?
Hence distance= speed x time
= 10 km/hr x 5 sec. (SI units are mismatching)
= 10 x(1000/3600) m/s x 5 s (SI units are matching0
= 10 x (5/18) x 5 m
=125/9 meters answer//
for example speed= 10km/hr
and time = 5 sec.
Then to find distance in meters..... How will you calculate?
Hence distance= speed x time
= 10 km/hr x 5 sec. (SI units are mismatching)
= 10 x(1000/3600) m/s x 5 s (SI units are matching0
= 10 x (5/18) x 5 m
=125/9 meters answer//
Sarvepalli.rajasekhar said:
1 decade ago
Dear Vidya and Praveen raj you first try to understand the problem logically.
When a train is halfway the bridge we say that the train is on the bridge.
We say that a train has crossed the bridge when the last compartment has crossed which means the total distance travelled by the train will be its own length completely and the bridge length.
When a train is halfway the bridge we say that the train is on the bridge.
We say that a train has crossed the bridge when the last compartment has crossed which means the total distance travelled by the train will be its own length completely and the bridge length.
Jyoti said:
9 years ago
Train takes 25/2 sec to travel 360 m, then how it's possible that it is taking same 25/2 sec to travel 500 m as well if it takes 25/2 sec for 360 m then it should take x sec to travel 500 m and then cross multiply and get value of x and that will be time taken to travel 500 m.
Am I right? Please explain.
Am I right? Please explain.
Sikkanthar said:
1 decade ago
It is very simple problem.
Here we are going to calculate the value of the time.
All we know the distance or length is nothing but (train length + platform length) from this value we can calculate the time value like.
Length/speed = time.
Convert the speed value m/s into kmph.
Here we are going to calculate the value of the time.
All we know the distance or length is nothing but (train length + platform length) from this value we can calculate the time value like.
Length/speed = time.
Convert the speed value m/s into kmph.
Samama Javaid said:
1 year ago
Speed of train = v = 45km/h = 45 × 1000/3600 = 25/2 m/s,
Length of Train= S¹= 360m,
Length of Bridge=S²= 140 m,
Time taken = t1= ?
Time taken = t2=?
Solution :
t1 = S¹/v = 360×2/25 = 28.8 s.
t2 = S2/v = 140 × 2/25= 11.2 s.
Total time taken = t1 + t2= 28.8 + 11.2.
t= 40s.
Length of Train= S¹= 360m,
Length of Bridge=S²= 140 m,
Time taken = t1= ?
Time taken = t2=?
Solution :
t1 = S¹/v = 360×2/25 = 28.8 s.
t2 = S2/v = 140 × 2/25= 11.2 s.
Total time taken = t1 + t2= 28.8 + 11.2.
t= 40s.
(4)
Dheeraj said:
5 years ago
Here length of train =360m.
Length of bridge =140m.
Speed of train =45km/h.
To convert into m/s multiplying it with 5/18.
Now to find time=Distance/speed.
Distance=length of both train and bridge.
Distance=140+360.
Speed=45*5/18=25/2.
Time=500/25/2=500*2/25=40.
Length of bridge =140m.
Speed of train =45km/h.
To convert into m/s multiplying it with 5/18.
Now to find time=Distance/speed.
Distance=length of both train and bridge.
Distance=140+360.
Speed=45*5/18=25/2.
Time=500/25/2=500*2/25=40.
(7)
Madhav Kulkarni said:
6 years ago
Train Length=360 Speed=45km/h=45*(5/18)=12.15m/s.
So Train Speed is 12.15m/s.
Bridge Length = 140.
Speed = Distance/Time.
12.15 = 360+140/time.
Time = 360+140/12.15.
= 500/12.5.
= 40.
So, the Time Require to cross 140m Bridge is 40sec.
So Train Speed is 12.15m/s.
Bridge Length = 140.
Speed = Distance/Time.
12.15 = 360+140/time.
Time = 360+140/12.15.
= 500/12.5.
= 40.
So, the Time Require to cross 140m Bridge is 40sec.
(5)
Hardik Patel said:
9 years ago
@Shruthi.
140m is a only bridge length.
If you consider only 140 m length it means only first point of train cross a bridge not whole train.
If you add a 340 m(length of the train) in 140m it means the whole train cross the bridge.
so add (360+140).
140m is a only bridge length.
If you consider only 140 m length it means only first point of train cross a bridge not whole train.
If you add a 340 m(length of the train) in 140m it means the whole train cross the bridge.
so add (360+140).
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