The diameter of each wheel of a car is $70 \, cm$. If each wheel rotates $400 \, \text{times per minute}$, then the speed of the car (in $km/hr$) is $\left( \text{Take } \pi = \frac{22}{7} \right)$.

$A$ 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 $\text{minutes}$)

Two men $A$ and $B$ start from a place $P$ walking at $3 \, km/h$ and $3.5 \, km/h$ respectively. How many $km$ will they be apart at the end of $3 \, h$,if they walk in opposite directions (in $.5$)?

$A$ 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 time taken by them is $14 \, hours$. Then $A$'s speed is equal to (in $km/hr$)

Robert is travelling on his cycle and has calculated to reach point $A$ at $2\, p.m.$ if he travels at $10 \,km/hr$; he will reach there at $12\, noon$ if he travels at $15\, km/hr$. At what speed must he travel to reach $A$ at $1\, p.m.$? (in $km/hr$)

$A$ man is walking at a speed of $10 \, km/h$. After every $1 \, km$, he takes a rest for $5 \, minutes$. How much time will he take to cover a distance of $5 \, km$? (in $minutes$)