Question

A car travels $1/3$ of the distance on a straight road with a velocity of $10km/h$, next one-third with a velocity of $20km/h$ and the last one third with a velocity of $60km/h$. Then the average velocity of the car (in km/h) during the whole journey is

• A. $30$
• B. $20$
• C. $18$
• D. $15$

Answer 1

Answer: (C)

$18$

$v_{avg}=\frac{TotalDistance}{Totaltime}$

Total Distance $=S$

$v_{avg}=\frac{S}{\frac{S}{3\times 10}+\frac{S}{3\times 20}+\frac{S}{3\times 60}}$

$v_{avg}=18m/sec$