Two trains 150 m and 120 m long respectively moving from opposite direction cross each other in 10 sec. If the speed of the second train is 43.2 km/hr, then the speed of the first train is :
A. 54 km/hr
B. 50 km/hr
C. 52 km/hr
D. 51 km/hr
Answer: Option A
Solution(By Examveda Team)
Let the speed of second train = x km/hrTheir relative speed in opposite direction :
= (43.2 + x) km/hr
According to the question,
$$\eqalign{ & {\text{Time = }}\frac{{{l_1} + {l_2}}}{{{\text{Speed}}}} \cr & \Rightarrow 10\sec = \frac{{\left( {150 + 120} \right){\text{m}}}}{{\left( {43.2 + x} \right) \times \frac{5}{{18}}{\text{ m/s}}}} \cr & \Rightarrow 10\sec = \frac{{270 \times 18}}{{\left( {43.2 + x} \right) \times 5}} \cr & \Rightarrow 43.2 \times 5 + 5x = 486 \cr & \Rightarrow x = \frac{{486 - 216}}{5} \cr & \Rightarrow x = 54 \cr} $$
∴ Speed of the second train = 54 km/hr
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
Join The Discussion