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Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - General Questions (Q.No. 23)
Problems on Trains
23.
Two trains are running in opposite directions with the same speed. If the length of each train is 120 metres and they cross each other in 12 seconds, then the speed of each train (in km/hr) is:
10
18
36
72
Answer: Option
Explanation:

Let the speed of each train be x m/sec.

Then, relative speed of the two trains = 2x m/sec.

So, 2x = (120 + 120)
12

=> 2x = 20

=> x = 10.

Therefore Speed of each train = 10 m/sec = ( 10 x 18 ( km/hr = 36 km/hr.
5

Discussion:
38 comments Page 4 of 4.
Priyanka said:   7 years ago
How the speed of both trains same?
(1)
Siva said:   6 years ago
How 18/5 came?
(1)
Stuti said:   5 years ago
S=D/T.
S=120/12= 10m/sec,
=10*(18/5)=36km/hr.
(2)
K. A. Raju said:   4 years ago
Distance to be covered by each train to cross each other is 60m. (Half of the length of each train).

Then, speed= 60/12 = 5 m/s = 18 km/hr.
(1)
Mike Lambulila said:   4 years ago
Where is 18/5 coming from?
(3)
Chris said:   4 years ago
speed=distance/time.
speed = 120/20,
then speed = 10 m/sec,
So, 10 x 18 /5.

Then the answer is 36 km/hr.
(2)
Keerthi said:   3 years ago
Let the speed of a single train be x m/sec.
length= 120m.
Time to cross each other= 12 sec.

There is a formula like,

a+b/u+v = time to cross each other,
(i.e) 120+120/2x = 12,
240/2x = 12,
X = 40.

= 40 * (18/5)hkm/hr,
= 144.

The Speed of each train is,
= 144/2.
= 72.
(1)
Saanvi S said:   2 years ago
S = D/S.
S = 120/12.
Therefore; S = 10 m/sec.
S = 10 × 18/5
And S = 36 kmph.
(6)
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