Q.
A car covers $AB$ distance with first one-third at velocity $v _{1} \,ms ^{-1}$, second one-third at $v _{2} \,ms ^{-1}$ and last one-third at $v _{3} \,ms ^{-1}$. If $v _{3}=3 v _{1}, v _{2}=2 v _{1}$ and $v _{1}=11 \,ms ^{-1}$ then the average velocity of the car is ______$ms ^{-1}$.
Solution: