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

The price of cooking oil has increased by $25 \%$. The percentage of reduction that a family should effect in the use of cooking oil,so as not to increase the expenditure on this account,is (in $\%$)

The number of students in a class is increased by $20 \%$ and the number now becomes $66$. Initially,the number was:

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 an examination,$30 \%$ and $35 \%$ students respectively failed in History and Geography while $27 \%$ students failed in both the subjects. If the number of students passing the examination is $248$,find the total number of students who appeared in the examination.

$25 \%$ of $25 \% = ?$