Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - General Questions (Q.No. 12)
12.
A goods train runs at the speed of 72 kmph and crosses a 250 m long platform in 26 seconds. What is the length of the goods train?
230 m
240 m
260 m
270 m
Answer: Option
Explanation:

Speed = 72 x 5 m/sec = 20 m/sec.
18

Time = 26 sec.

Let the length of the train be x metres.

Then, x + 250 = 20
26

x + 250 = 520

x = 270.

Discussion:
39 comments Page 4 of 4.

Savi said:   1 decade ago
Hi @Yogesh the formula is length=speed*time
here l=x*250
speed=72*5/18=20ms
time=26s
Apply formula
x+250=20*26
=520
Now got it

Yogesh said:   1 decade ago
x + 250 = 520, how 520 has come, please explain.

Sonia said:   1 decade ago
why x+250?.....for same direction we take sbtraction....then why it is added?

Ashok.K.Rathod said:   1 decade ago
Thanks dinesh.

Donald Pinto said:   1 decade ago
Hi Dinesh Thankyou so much for the explanation!!

Dinesh guptha said:   1 decade ago
Hi sonam,
Let me explain about converting km/hr into m/s in detail.

1 km = 1000 meters.
1 hr = 3600 seconds.

1 km/hr = 1000/3600 m/s

= 10/36 m/s

= 5/18 m/s.

Therefore 1 km/hr = 5/18 m/sec.
(1)

Sonam said:   1 decade ago
Ya. But why only 5/18 why not some other numbers?

Sania said:   1 decade ago
@ NISHA

Speed is given 72 kmps. But length of platform is in meters. so we have to change it into m/s.

Nisha dahiya said:   1 decade ago
Why 72 is multiplied by 5/18?


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