The population of a town increases by $2.5 \%$ annually but decreases by $0.5 \%$ every year due to migration. What will be the net percentage increase in population after $2$ years (in $\%$)?

In Convent Model School,$60 \%$ of the students are boys. In an aptitude test,$80 \%$ of the girls scored more than $40$ marks (out of a maximum possible $150$ marks). If $60 \%$ of the total students scored more than $40$ marks in the same test,find the fraction of the boys who scored $40$ marks or less?

The quantity of water needed to reduce $9 \ ml$ of shaving lotion containing $50 \%$ alcohol to a lotion containing $30 \%$ alcohol is: (in $ml$)

In two successive years,$80$ and $60$ students of a school appeared at the final examination,of which $60 \%$ and $80 \%$ passed respectively. The average rate of students passed (in percent) is

$A$ sum of $Rs$ $7,930$ is divided into $3$ parts and given on loan at $5 \%$ simple interest to $A, B$ and $C$ for $2, 3$ and $4$ years respectively. If the amounts (principal + interest) of all three are equal after their respective periods of loan,then the amount $A$ received as a loan is:

Two numbers are more than the third number by $20 \%$ and $80 \%$ respectively. The first number is what percent of the second number?