$23 \% \text{ of } 6783 + 57 \% \text{ of } 8431 = ?$

$A$ district has $64000$ inhabitants. If the population increases at the rate of $2 \frac{1}{2} \%$ per annum,then the number of inhabitants at the end of $3$ years will be...

What percentage of numbers from $1$ to $70$ have squares that end in the digit $1$?

If $120$ is $20 \%$ of a number,then $120 \%$ of that number will be

Christy donated $10 \%$ of his income to an orphanage and deposited $20 \%$ of the remainder in his bank. If he has now $Rs$ $7200$ left,what is his income?

If the given two numbers are respectively $7 \%$ and $28 \%$ of a third number,then what percentage is the first of the second?