$A$ man goes from a place $A$ to $B$ at a speed of $12 \, km/h$ and returns from $B$ to $A$ at a speed of $18 \, km/h$. The average speed for the whole journey is? (in $km/h$)

$A$ thief is spotted by a policeman from a distance of $400\, m$. When the policeman starts the chase,the thief also starts running. Assuming the speed of the thief is $5\, km/h$ and that of the policeman is $9\, km/h$,how far will the thief have run before he is overtaken by the policeman? (in $m$)

$A$ car travels $80 \, km$ in $2 \, hours$ and a train travels $80 \, km$ in $3 \, hours$. The ratio of the speed of the car to that of the train is

Two trains,each of length $90\, m,$ run on parallel tracks. When running in the same direction,the faster train passes the slower train completely in $18\, s,$ but when they are running in opposite directions approaching each other at the same speeds as before,they cross each other in $9\, s.$ Find the speed of each train (in $m/s$).

$A$ man covered a certain distance at some speed. Had he moved $3 \text{ km/hr}$ faster,he would have taken $40 \text{ minutes}$ less. If he had moved $2 \text{ km/hr}$ slower,he would have taken $40 \text{ minutes}$ more. The distance (in $\text{km}$) is:

$A$ truck covers a distance of $396 \, km$ in $5 \, hours \, 30 \, minutes$. The average speed of a bike is $\frac{4}{3}$ of the average speed of the truck. What is the time taken by the bike to cover a distance of $12 \, km$ less than the distance covered by the truck?