In covering a certain distance,the speeds of $A$ and $B$ are in the ratio of $3:4$. $A$ takes $30 \text{ minutes}$ more than $B$ to reach the destination. What is the time taken by $A$ to reach the destination (in hours)?

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

$A$ thief is noticed by a policeman from a distance of $200\, m$. The thief starts running and the policeman chases him. The thief and the policeman run at the speed of $10\, km/h$ and $11\, km/h$ respectively. What is the distance between them after $6\, minutes$? (in $m$)

$A$ person goes from point $A$ to $B$ with a speed of $55 \text{ km/hr}$ and returns with a speed of $65 \text{ km/hr}$. What is the average speed (in $\text{km/hr}$) of the person while going and coming back from $A$ to $B$?

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

Heena and Renu are competing in a $100\, m$ race. Initially,Heena runs at twice the speed of Renu for the first $50\, m$. After the $50\, m$ mark,Heena runs at $\frac{1}{4}$ of her initial speed,while Renu continues to run at her original speed. If Renu catches up with Heena at a distance of $N$ meters from the finish line,then $N$ is equal to (in meters).