The average of $100$ observations was calculated as $35$. It was found later that one of the observations was misread as $83$ instead of $53$. The correct average is: (in $.7$)

The average age of $6$ members of a family is $20$ years. If the age of a servant is included,the average age increases by $25\%$. What is the age (in years) of the servant?

The average marks obtained by a class of $60$ students is $65$. The average marks of half of the students is found to be $85$. The average marks of the remaining students is:

The average of runs of a cricket player in $10$ innings was $32$. How many runs must he make in his next innings so as to increase his average of runs by $4$?

Amitabh's average expenditure from $January$ to $June$ is $Rs. 4200$. He spends $Rs. 1200$ in $January$ and $Rs. 1500$ in $July$. What is the average expenditure for the months of $February$ to $July$ (in $Rs.$)?

The average salary of the entire staff in an office is $Rs. 120$ per month. The average salary of officers is $Rs. 460$ and that of non-officers is $Rs. 110$. If the number of officers is $15$,then find the number of non-officers in the office?