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:
200 m
225 m
245 m
250 m
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 5 of 25.

Anshul patel said:   1 decade ago
Amasing solutions and discussion by you guys but 1 thing I got in mind while coming through few examples is that if some1 is new in solving this type of problems then please draw 1 rough imaginary sketch and then try to solve this type of examples I prefer it to be more easy.

Rohit said:   1 decade ago
Please help me,

When the train crosses the bridge, shouldn't we consider the length of the train after the bridge also.

All above solutions are only by considering the start point of the train.

And if only that is considered then what is the use of the length of the train.

Mahes said:   1 decade ago
I have solved this problem in a different way, is this right way to solve?

Speed = 25/2 m/sec

Length of the bridge be x m.

Total distance = Speed * Time

x + 130 = 30 * 25/2
x + 130 = 375
x = 245 m

Is the above method to solve this problem right?

Please explain.

Sivakumar.s said:   1 decade ago
Train 130 meters long. Travel 45 km/hr.

To convert m/s = 25/2.

So 2 second train will move 25 meter. So 30 second means.

2*15 = 30 second.

25*15 = 375.

So train travelling 375 meters to reduce the train meters.

375-130 = 245.

So the bridge meter is 245 meters.
(1)

Rajeev R T said:   1 decade ago
If the train is travelling 45 km per hr, then in one min.it can travel 750m, and in 1 sec it can travel 12.5m. then in 30 sec it can travel 375.00 m. As in 375m the length of the train is included, deduct the length of the train from the 375.00m, i.e 245.00m.

Nusrat fathima said:   2 decades ago
Hi Uvitha,



Speed=25/2 m/sec



then we find the lenght of the bridge using the formula



distance/time = speed



where distance = length of train + x



Time = 30 sec & speed = 25/2



130 + x 25

------- = --

30 2


=> 245 m

Rajesh said:   8 years ago
Length= speed * time.

Let the bridge length is 'x' and that x is add to train length.
So 130 + x.
As per formula:
(130+x ) =(45 * {1000/3600}) * 30
=( 45 * (5/18) ) * 30
= (750/2)
(130+x) = 375
x = 375-130
x = 245
x = 245.

Nusrat fathima said:   2 decades ago
I have solved this problem in a different way, is this right way to solve?
speed=25/2 m/sec
length of the bridge be x m
total distance = speed * time
x + 130 = 30 * 25/2
x + 130 = 375
x = 245 m
is the above method to solve this problem right?

Please help.
(1)

Amar said:   10 years ago
Train length bridge length train length.

Logically we should add train twice the train length, since crossing the bridge means train is not yet on the bridge and then it should be rolled off from bridge?

i.e , (x+2*130)/30 = 55 km/hr.

What say?

Fearless said:   4 months ago
The speed of train in sec = 45000/3600 = 12.5sec.
distance travel by train in 30 sec = 12.5 * 30 = 375m,
lenght of train = 130m.
Length of bridge = distance traveled by the train - length of train.
= 375-130 = 245m.
(41)


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