A train travelling at 48 kmph crosses another train, having half of 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 railway platform is:
A. 200m
B. 300m
C. 350m
D. 400m
Answer: Option D
Solution(By Examveda Team)
Let the length of the train traveling at 48 kmph be 2x meters. And length of the platform is y meters.$$\eqalign{ & {\text{Relative speed of train}} \cr & = \left( {48 + 42} \right)\,{\text{kmph}} \cr & = {\frac{{90 \times 5}}{{18}}} \cr & = 25\,m/\sec \cr & {\text{And}}\,{\text{48}}\,{\text{kmph}} \cr & = \frac{{48 \times 5}}{{18}} \cr & = \frac{{40}}{3}\,m/\sec \cr & \cr & {\text{According to the question}}, \cr & \frac{{ {2x + x} }}{{25}} = 12; \cr & Or,\,3x = 12 \times 25 = 300 \cr & Or,\,x = \frac{{300}}{3} = 100m \cr & {\text{Then, length of the train}} \cr & = 2x \cr & = 100 \times 2 = 200m \cr & \frac{{200 + y}}{{ {\frac{{40}}{3}} }} = 45 \cr & 600 + 3y = 40 \times 45 \cr & {\text{Or}},\,3y = 1800 - 600 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 1200 \cr & {\text{Or}},\,y = \frac{{1200}}{3} = 400m \cr & {\text{Length of the platform}} \cr & = 400m \cr} $$
Join The Discussion
Comments ( 3 )
Related Questions on Speed Time and Distance
A. 48 min.
B. 60 min.
C. 42 min.
D. 62 min.
E. 66 min.
A. 262.4 km
B. 260 km
C. 283.33 km
D. 275 km
E. None of these
A. 4 hours
B. 4 hours 30 min.
C. 4 hours 45 min.
D. 5 hours
Ans Is 200
Relative speed=48+42=90kmph
S=vt=90×1000×12/3600
so distance,S=300m
as 2 nd train is half in length so 1st train length should twice so 1st train length is 200m
Let,station distance is Y
so train have to pass(200+Y) distance is 45 s with velocity 48 kmph
so,(200+Y)=48kmph×45s=48×1000×45/3600 (m/s×s)
Y=400m
(200+y)/40/3=45
Hw this ???pls explain