Find the average of all the numbers between $6$ and $34$ which are divisible by $5$.

The average of six numbers is $20$. If one number is removed,the average becomes $15$. What is the number removed?

The average age of a husband and wife,who were married $7 \, \text{years}$ ago,was $25 \, \text{years}$ at the time of their marriage. Now,the average age of the family,including the husband,wife,and a child born during the interval,is $22 \, \text{years}$. What is the present age of the child in $\text{years}$?

David obtained $76, 65, 82, 67$ and $85$ marks (out of $100$) in English,Mathematics,Physics,Chemistry,and Biology. What is his average marks?

The mean of marks secured by $50$ students in division $A$ of class $X$ is $61$,$25$ students of division $B$ is $57$,and that of $50$ students of division $C$ is $55$. What will be the mean of marks of the students of three divisions of Class $X$?

The average of $6$ numbers is $3.95$. The average of two of them is $3.4$,while the average of the other two is $3.85$. What is the average of the remaining two numbers?