If $60 \%$ of the students in a school are boys and the number of girls is $812$,how many boys are there in the school?

The sum of two numbers is $2490$. If $6.5\%$ of one number is equal to $8.5\%$ of the other,then the numbers are:

In measuring the sides of a rectangle,one side is taken $10 \%$ in excess and the other $20 \%$ in deficit. Find the error per cent in area calculated from the measurement.

An empty fuel tank of a car was filled with an ordinary type of petrol. When the tank was one-third empty,it was filled with high-speed petrol. Again,when the tank was one-third empty,it was filled with an ordinary type of petrol. Again,when the tank was one-third empty,it was filled with high-speed petrol. At this time,what was the percentage of high-speed petrol in the tank?

If $8 \%$ of the people eligible to vote are between $18$ and $21$ years of age,and in an election,$85 \%$ of those eligible to vote who were between $18$ and $21$ years of age actually voted,then the number of persons between $18$ and $21$ years of age who actually voted is what percent of the total people eligible to vote?

When a number is divided by $12$,the quotient is $\frac{1}{4}$ of another number. By what percentage is the first number greater than the second number?