The average of three numbers,of which the greatest is $16$,is $12$. If the smallest is half of the greatest,what is the remaining number?

The average of the first nine prime numbers is

The average age of students of a class is $15.8 \text{ years}$. The average age of boys in the class is $16.4 \text{ years}$ and that of the girls is $15.4 \text{ years}$. The ratio of the number of boys to the number of girls in the class is:

Fifteen movie theatres average $600$ customers per theatre per day. If $six$ of the theatres close down but the total theatre attendance stays the same,then the average daily attendance per theatre among the remaining theatres is:

The average weight of $24$ students is $35\, kg$. If the weight of the teacher is added, the average increases by $400\, g$. What is the weight of the teacher in $kg$?

The mean marks of $10$ boys in a class is $70 \%$,whereas the mean marks of $15$ girls is $60 \%$. The mean marks of all the $25$ students is