Train

3. A train travelling at 48 kmph completely crosses another train having half its length and travelling in opposite direction at 42 kmph, in 12 seconds. It also passes a railway platform in 45 seconds. The length of the platform is

[A]. 400 m
[B]. 450 m
[C]. 560 m
[D]. 600 m
✅ The correct answer is option A.
Let the length of the first train be x metres.

Then, the length of the second train is

x

metres.

2

Relative speed = (48 + 42) kmph =

90 x
5

m/sec = 25 m/sec.

18

[x + (x/2)]
= 12 or
3x
= 300     or     x = 200.

25
2

Length of first train = 200 m.
Let the length of platform be y metres.

Speed of the first train =

48 x
5

m/sec =
40
m/sec.

18
3

(200 + y) x
3
= 45

40

600 + 3y = 1800
y = 400 m.

10. A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is:

[A]. 45 m
[B]. 50 m
[C]. 54 m
[D]. 72 m
✅ The correct answer is option B.
2 kmph =

2 x
5

m/sec =
5
m/sec.

18
9

4 kmph =

4 x
5

m/sec =
10
m/sec.

18
9

Let the length of the train be x metres and its speed by y m/sec.

Then,

x

= 9 and

x

= 10.

y –
5

9

y –
10

9

9y – 5 = x and 10(9y – 10) = 9x
9y – x = 5 and 90y – 9x = 100.
On solving, we get: x = 50.
Length of the train is 50 m.

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