Is it possible for a moving object to have a constant velocity and a changing speed?

The ratio of the numerical values of the average velocity and average speed of a body is always

$A$ body has speed $V, 2V$ and $3V$ in the first $1/3$ of distance $S$,second $1/3$ of $S$,and third $1/3$ of $S$ respectively. Its average speed will be:

$A$ particle moves with constant speed $v$ along a regular hexagon $ABCDEF$ in the same order. What is the magnitude of the average velocity for its motion from $A$ to $F$?

$A$ man walks on a straight road from his home to a market $2.5 \,km$ away with a speed of $5 \,km/h$. Finding the market closed,he instantly turns and walks back home with a speed of $7.5 \,km/h$. The average speed of the man over the interval of time $0$ to $40 \,min$ is equal to

$A$ vehicle travels half the distance with speed $v$ and the remaining distance with speed $2v$. Its average speed is: