Two litres of water evaporate from $10$ litres of a solution containing $10 \%$ salt. The percentage of salt in the remaining solution is

In a certain school,$20 \%$ of students are below $8$ years of age. The number of students above $8$ years of age is $\frac{2}{3}$ of the number of students of $8$ years age,which is $48$. What is the total number of students in the school?

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 $75 \%$ of a number is $380$ more than $35 \%$ of the same number. What is $20 \%$ of that number?

$A$ student multiplied a number by $\frac{3}{5}$ instead of $\frac{5}{3}$. What is the percentage error in the calculation?

Sunil decided to donate $5 \%$ of his salary. On the day of donation,he changed his mind and donated $₹ 1687.50$,which was $75 \%$ of what he had decided earlier. How much is Sunil's salary?