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 3 of 8.
Rajkumar velu said:
1 decade ago
Hi saranya,
When the two length is there,
We use the formula for time=(length1+length2)/speed
Speed=45*5/18=25/2 m/sec
So, t=(360+140)/25/2
t=500*2/25
t=40 sec
When the two length is there,
We use the formula for time=(length1+length2)/speed
Speed=45*5/18=25/2 m/sec
So, t=(360+140)/25/2
t=500*2/25
t=40 sec
Vidhya said:
1 decade ago
I understand the problem. But why we add 360+140. Explain.
PraveenRaj said:
1 decade ago
I don't understand why in every problem they adding the train length also which they not asked. ?
Issacnewton said:
1 decade ago
Hi everybody,
See when a train crosses a platform/bridge, it (train) has to cross.
The length of the platform/bridge as well as its own length4.
Length of the train+platform we should take to solve the problem.
See when a train crosses a platform/bridge, it (train) has to cross.
The length of the platform/bridge as well as its own length
Length of the train+platform we should take to solve the problem.
Ashok Reddy said:
1 decade ago
t=distance/speed;
t=500/(45*5/18);
t=40sec
t=500/(45*5/18);
t=40sec
Sarvepalli.rajasekhar said:
1 decade ago
Speed = 45 km / hr = 45 x 1000 / 3600 = 25/2 meters per second.
Total Length = Length of train + bridge = 360+140 = 500 meters.
Time = ?
speed = distance / time
25 / 2 = 500 / y
25/2 x y = 500
y = 500 / (25/2) = 500 x 2/25 = 1000/25 = 40 seconds.
Total Length = Length of train + bridge = 360+140 = 500 meters.
Time = ?
speed = distance / time
25 / 2 = 500 / y
25/2 x y = 500
y = 500 / (25/2) = 500 x 2/25 = 1000/25 = 40 seconds.
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.
Anonymus said:
1 decade ago
Nice sarvepalli great explanation. I got.
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//
Gaurav said:
1 decade ago
Total length = bridge length + train length = 140+360=500.
Let time taken by train be x.
Then,
500/x=45*5/18 m/sec.
500/x=25/2.
1000=25x.
x=40 sec answer.
Let time taken by train be x.
Then,
500/x=45*5/18 m/sec.
500/x=25/2.
1000=25x.
x=40 sec answer.
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