Question
CIVICS > ELECTION_COMMISSION
1) A car covers a certain distance at 90 km/hour speed and returns back to the starting point at 60 km/hour speed. Find its average speed for the entire journey
A) 70 km/hourB) 72 km/hour
C) 75 km/hourD) 80 km/hour
View Answer        RRB Se Exam 2014 yellow colour
Answer : 72 km/hour

egin{aligned}\ ext{Average speed of the car}=frac{2xy}{(x+y)} frac{km}{hr}\ =frac{2*90*60}{(90+60)}\ =frac{2*5400}{150}\ =36*2\ Avg.Speed=72\ end{aligned}



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