$A$ car covers $2/5^{th}$ of the total distance with speed $v_1$ and $3/5^{th}$ of the total distance with speed $v_2$. What is its average speed?

$A$ 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

$A$ particle moves along a semicircle of radius $10\,m$ in $5$ seconds. The average velocity of the particle is...........$m/s$.

$A$ 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

$A$ 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............$km/hr$

$A$ car travels in a straight line along a road. Its distance $x$ from a stop sign is given as a function of $t$ by the equation $x(t) = \alpha t + \beta t^3$, where $\alpha = 2.0 \ m \ s^{-1}$ and $\beta = 0.01 \ m \ s^{-3}$. Calculate the average velocity of the car in the time interval $t = 2.00 \ s$ to $t = 4.00 \ s$. (in $m \ s^{-1}$)