Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction?
A. 10
B. 12
C. 15
D. 20
Answer: Option B
Solution(By Examveda Team)
$$\eqalign{ & {\text{Speed}}\,{\text{of}}\,{\text{the}}\,{\text{first}}\,{\text{train}} \cr & = {\frac{{120}}{{10}}} \,{\text{m/sec}} \cr & = 12\,{\text{m/sec}} \cr & {\text{Speed}}\,{\text{of}}\,{\text{the}}\,{\text{second}}\,{\text{train}} \cr & {\frac{{120}}{{15}}} \,{\text{m/sec}} \cr & = 8\,{\text{m/sec}} \cr & {\text{Relative}}\,{\text{speed}} = {12 + 8} = 20\,{\text{m/sec}} \cr & \therefore {\text{Required}}\,{\text{time}} \cr & = {\frac{{ {120 + 120} }}{{20}}} \,{\text{ sec}} \cr & = 12\,{\text{sec}} \cr} $$Related Questions on Problems on Trains
A. 120 metres
B. 180 metres
C. 324 metres
D. 150 metres
A. 45 km/hr
B. 50 km/hr
C. 54 km/hr
D. 55 km/hr
A. 200 m
B. 225 m
C. 245 m
D. 250 m
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