$A$ 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 moves in the east direction with $15 \, m/s$ for $2 \, s$,then moves northward with $5 \, m/s$ for $8 \, s$. The average velocity of the particle is:

$A$ car travels the first half of a distance between two places at a speed of $30 \, km/hr$ and the second half of the distance at $50 \, km/hr$. The average speed of the car for the whole journey is .......... $km/hr$.

$A$ 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

$A$ car moves from $A$ to $B$ with a speed of $30 \ km/h$ and from $B$ to $A$ with a speed of $20 \ km/h$. What is the average speed of the car (in $km/h$)?

$A$ car moves for half of its time at $80 \, km/h$ and for the rest half of the time at $40 \, km/h$. The total distance covered is $60 \, km$. What is the average speed of the car in $km/h$?