What percent of Rs. $2650$ is Rs. $1987.50$?

$A$'s salary is $40 \%$ of $B$'s salary,which is $25 \%$ of $C$'s salary. What percentage of $C$'s salary is $A$'s salary?

$0.01$ is what percent of $0.1$?

What fraction is $0.6 \%$?

Out of $450$ students of a school,$325$ play football,$175$ play cricket and $50$ neither play football nor cricket. How many students play both football and cricket?

$A$ speaks truth in $80 \%$ of the cases and $B$ in $90 \%$ of the cases. Find the percentage when they contradict each other in describing the same facts. (in $\%$)