If $10 \%$ of $x = 20 \%$ of $y,$ then $x : y$ is equal to

The ratio of ages between $A$ and $B$ is $6: 5$ and the age of each $C$ and $D$ is $\frac{9}{10}$ times that of $B$. The age of $F$ is less than $A$ but greater than $B$. The ratio of ages between $B$ and $E$ is $2: 3$. Also,the age of $A$ is $3 \text{ years}$ less than $E$. What is the ratio of the ages of $A$ and $F$ if all the ages are integers?

In a mixture of $60 \, \text{litres}$,the ratio of milk and water is $2:1$. What amount of water (in $\text{litres}$) must be added to make the ratio of milk and water $1:2$?

In a class there are $z$ students. Out of them $x$ are boys. What part of the class is composed of girls?

₹ $11,550$ has to be divided between $X$,$Y$,and $Z$ such that $X$ gets $\frac{4}{5}$ of what $Y$ gets and $Y$ gets $\frac{2}{3}$ of what $Z$ gets. How much more does $Z$ get over $X$ (in ₹)?

If $U: V = 6: 7$ and $V: W = 21: 6$,then find $U: V: W$.