IBPS RRB Office Assistant 20 Sep 2015 Paper

(5) Speed of train A = 63 kmph = (63×518 ) m / sec ‌
=17.5 m / sec ‌
Speed of train B=54 kmph
= (

54×5

18

) m / sec ‌
=15 m / sec‌
If the length of train A be x metre, then
Speed of train A
=
=

Length of train and platform

Time taken in crossing

⇒17.5=

x+199.5

21

⇒17.5×21=x+199.5
⇒367.5=x+199.5
⇒x=367.5−199.5=168 metre
Case II
Relative speed
= (17.5 + 15) = 32.5 m/sec.
∴ Required time
=

Length of trains A and B

Relative speed

=(

168+157

32.5

) seconds
=

325

32.5

=10 seconds