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?
40 sec
42 sec
45 sec
48 sec
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.

Sameena kabir said:   7 years ago
Please, anyone can solve this one I can't understand how to tackle this one?

A train travell 34 km in 54mints. How far a train travell in 60 mints.

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).

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.

Aishwarya said:   9 years ago
What about this?

Let time be x sec.
Length of the train = 360/x,
Length of the bridge = 140m,
Required time = (360+140)/x,
Which is , x = 500m,
Speed= (45 * 5/18) = 25/2 m/sec,
Time = distance/ time,
500 * 25/2 = 40sec.

Is this method right?

Uzair said:   9 years ago
What about this?

What is the speed of a 140 m long train cross a 1 km bridge in 12 sec?

Shruthi Bhosle said:   9 years ago
We should find time only for distance of 140m long, why we add (360 + 140).

Sujith kumar said:   9 years ago
Speed = 45km/hr = 45 * 1000/60 * 60 = 12.5m/ec.
Length = Speed * Time.

360 + 140 = 12.5 * time.
Time = 500/12.5 = 40sec.
(1)

Anonymous said:   9 years ago
In this question, the length of the bridge is shorter than that of the train. Then why we go for adding the two lengths?

Virang soni said:   9 years ago
d = s * t = 45 * (5/18) = 12.5.

Total length = 360 + 140/12.5 = 40.

PANASA HARISH KUMAR said:   9 years ago
Train long = 360m.
Speed 45*5/18 = 12.5m/sec.
Bridge long = 140m.
Time = ?

Speed = Distance/Time
12.5 = 360 + 140/time.
Time = 40sec.


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