The average marks of a student obtained in Physics,Chemistry,and Biology is $70.$ If the student obtained $90$ marks in Mathematics,then the new average is

The average age of a family of $6$ members is $22 \text{ years}$. If the age of the youngest member is $7 \text{ years}$,then what was the average age of the family at the birth of the youngest member?

The average of odd numbers up to $100$ is?

The average salary,per head,of all the workers of an institution is $Rs.\, 60$. The average salary of $12$ officers is $Rs.\, 400$; the average salary,per head,of the rest is $Rs.\, 56$. The total number of workers in the institution is:

$16$ children are to be divided into two groups $A$ and $B$ of $10$ and $6$ children. The average percent marks obtained by the children of group $A$ is $75$ and the average percent marks of all the $16$ children is $76$. What is the average percent marks of children of group $B$?

What is the average of all numbers between $8$ and $74$ which are divisible by $7\, ?$