Is the average of different speeds called average speed? Do you agree?

$A$ train travels from city-$A$ to city-$B$ with a constant speed of $18 \,ms^{-1}$ and returns back to city-$A$ with a constant speed of $36 \,ms^{-1}$. Find its average speed during the journey. (in $\,ms^{-1}$)

$A$ particle travels half of the distance of a straight journey with a speed $6 \,m/s$. The remaining part of the distance is covered with speed $2 \,m/s$ for half of the time of the remaining journey and with speed $4 \,m/s$ for the other half of the time. The average speed of the particle is ....... $m/s$.

$A$ bus travels the first one-third distance at a speed of $10\; km/h$,the next one-third at $20\; km/h$,and the last one-third at $60\; km/h$. The average speed of the bus is ........ $km/h$.

"The magnitude of average velocity is equal to average speed". This statement is not always correct and not always incorrect. Explain with an example.

$A$ 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