$A$ car travels from $A$ to $B$ at a speed of $20\,km/hr$ and returns at a speed of $30\,km/hr$. The average speed of the car for the whole journey is............$km/hr$

Give the difference between average speed and average velocity.

$A$ person goes from point $P$ to point $Q$ covering $1/3$ of the distance with speed $10 \, km/h$,the next $1/3$ of the distance at $20 \, km/h$,and the last $1/3$ of the distance at $60 \, km/h$. The average speed of the person is ............ $km/h$.

$A$ car travels a distance $S$ on a straight road in two hours and then returns to the starting point in the next three hours. Its average velocity is

$A$ train has a speed of $60\, km/h$ for the first one hour and $40\, km/h$ for the next half hour. Its average speed in $km/h$ is

$A$ vehicle runs on a straight road of length $L$. It travels half the distance with speed $V$ and the remaining distance with speed $\frac{V}{3}$. Its average speed is