$A$ man driving at $\frac{3}{4}$ of his original speed reaches his destination $20 \text{ minutes}$ later than the usual time. Then the usual time is (in $\text{minutes}$)

$A$ train running at the speed of $84 \, km/h$ passes a man walking in the opposite direction at the speed of $6 \, km/h$ in $4 \, s$. What is the length of the train (in $meters$)?

The speed of a train going from Nagpur to Allahabad is $100 \text{ km/h}$,while its speed is $150 \text{ km/h}$ when coming back from Allahabad to Nagpur. What is the average speed during the whole journey in $\text{km/h}$?

$A$ is faster than $B$. $A$ and $B$ each walk $24 \, km$. The sum of their speeds is $7 \, km/hr$ and the sum of the times taken by them is $14 \, hours$. Then $A$'s speed is equal to (in $km/hr$):

$A$ 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?

$A$ bus travels $720 \text{ km}$ in $20 \text{ hours}$. Calculate its average speed in $\text{metres/seconds}$.