$A$ 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 $km/h$)

Ramesh crosses a $600 \, m$ long street in $5 \, \text{minutes}$. His speed in $km/h$ is:

$A$ man covers a certain distance by car driving at $70 \, km/hr$ and he returns to the starting point riding on a scooter at $55 \, km/hr$. Find his average speed for the whole journey in $km/hr$.

$A$ man walking at the rate of $5\, km/hr$ crosses a bridge in $15\, minutes$. The length of the bridge (in $meters$) is:

$A$ person travels from $P$ to $Q$ at a speed of $40 \, km/hr$ and returns by increasing his speed by $50 \%$. What is his average speed for both the trips? (in $km/hr$)

$A$ car driver leaves Bangalore at $8:30 \, am$ and expects to reach a place $300 \, km$ from Bangalore at $12:30 \, pm$. At $10:30 \, am$, he finds that he has covered only $40 \%$ of the distance. By how much does he have to increase the speed of the car in order to keep up with his schedule? (in $km/h$)