Find the third proportional to the numbers $4$ and $42$.

The third proportional of $12$ and $18$ is

$85 \, L$ of a mixture contains milk and water in the ratio $27: 7$. How much more water (in $L$) is to be added to get a new mixture containing milk and water in the ratio $3: 1$?

The ratio of the present ages of Suresh and Mahesh is $7:5$. If after $6$ years their ages will be in the ratio of $4:3$,the present age of Mahesh is (in $years$):

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

Two numbers are respectively $20 \%$ and $50 \%$ more than a third number. The ratio of the two numbers is