$A$ man can reach a certain place in $30 \, h$. If he reduces his speed by $\frac{1}{15}^{th}$,he goes $10 \, km$ less in that same time. Find his speed in $km/h$.

$A$ motorcyclist left $6 \frac{2}{3}$ minutes later than the scheduled time,but in order to reach his destination $21 \, km$ away on time,he had to increase his speed by $12 \, km/h$ from his usual speed. What is the usual speed (in $km/h$) of the motorcyclist?

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

$A$ goods train and a passenger train are running on parallel tracks in the same direction. The driver of the goods train observes that the passenger train coming from behind overtakes and crosses his train completely in $60 \, s$. Whereas a passenger on the passenger train marks that he crossed the goods train in $40 \, s$. If the speeds of the trains are in the ratio of $1:2$,find the ratio of their lengths.

$A$ man leaves a point $P$ and reaches the point $Q$ in $4 \, hours$. Another man leaves the point $Q$,$2 \, hours$ earlier and reaches the point $P$ in $4 \, hours$. Find the time in which the first man meets the second man (in $hours$).

Flight $A$ usually takes $1 \, \text{hour}$ more than Flight $B$ to travel a distance of $7200 \, \text{km}$. Due to engine trouble,the speed of Flight $B$ decreases by a factor of $\frac{1}{6}$,so it takes $36 \, \text{minutes}$ more than Flight $A$ to complete the same journey. What is the speed of Flight $A$ (in $\text{km/hr}$)?