The ratio of boys and girls in a school is $9:5$. If the total number of students in the school is $1050$,then the number of boys is

$A$ mixture contains alcohol and water in the ratio $4:3$. If $5 \text{ liters}$ of water is added to the mixture,the ratio becomes $4:5$. Find the quantity of alcohol in the given mixture (in $\text{L}$).

If $6 A = 4 B = 9 C$,what is $A : B : C$?

The monthly salaries of $A, B$ and $C$ are in the ratio $2: 3: 5$. If $C$'s monthly salary is $Rs. 12000$ more than that of $A$,then $B$'s annual salary is (in $Rs.$):

Three containers have volumes in the ratio $3:4:5$. They are full of mixtures of milk and water. The mixtures contain milk and water in the ratio of $4:1$,$3:1$,and $5:2$ respectively. The contents of all these three containers are poured into a fourth container. The ratio of milk and water in the fourth container is

If $x: y = 2: 1,$ then $(x^{2} - y^{2}) : (x^{2} + y^{2})$ is