$A$ boy rides his bicycle $10 \, km$ at an average speed of $12 \, km/hr$ and again travels $12 \, km$ at an average speed of $10 \, km/hr$. His average speed for the entire trip is approximately (in $km/hr$)

Buses start from a bus terminal with a speed of $20 \text{ km/h}$ at intervals of $10 \text{ mins}$. What is the speed of a man coming from the opposite direction towards the bus terminal if he meets the buses at intervals of $8 \text{ mins}$? (in $\text{km/h}$)

$A$ man goes from $A$ to $B$ at a uniform speed of $12 \, km/h$ and returns with a uniform speed of $4 \, km/h$. His average speed (in $km/h$) for the whole journey is?

Two trains are moving in the same direction at $50 \, km/h$ and $30 \, km/h$. The faster train crosses a man in the slower train in $18 \, seconds$. Find the length of the faster train (in $m$).

$A$ train passes through a telegraph post in $9$ $seconds$ moving at a speed of $54 \, km/h$. The length of the train is (in $meters$):

$A$ 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