The ratio of the present ages of $R$ and $S$ is $11:17$. $11$ years ago,the ratio of their ages was $11:20$. What is $R$'s present age (in years)?

The ratio of the number of boys to girls in an institution is $6:5$. If there are $192$ boys in total,find the total number of students in the institution.

The respective ratio between the speeds of a car,a jeep,and a tractor is $3:5:2$. The speed of the jeep is $250\%$ of the speed of the tractor,which covers $360 \text{ km}$ in $12 \text{ hours}$. What is the average speed of the car and the jeep together in $\text{km/h}$?

Three vessels having volumes in the ratio of $2: 3: 5$ are full of a mixture of water and milk. In the first vessel,the ratio of water and milk is $1: 3$,in the second $2: 3$,and in the third vessel,$2: 5$. If all the three vessels are poured into a large container,what is the resulting ratio of milk and water?

$A, B, C$ and $D$ purchase a gift worth $Rs. 60$. $A$ pays $\frac{1}{2}$ of what others are paying,$B$ pays $\frac{1}{3}$ of what others are paying,and $C$ pays $\frac{1}{4}$ of what others are paying. What is the amount paid by $D$?

The sum of two numbers is $25$ and their difference is $7 \frac{1}{2}$. Find the ratio of the numbers.