The mean of $50$ observations was $36$. It was found later that an observation $48$ was wrongly taken as $23$. The corrected new mean 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 age of a class of $30$ students and a teacher reduces by $0.5 \, \text{years}$ if we exclude the teacher. If the initial average is $14 \, \text{years}$,find the age of the class teacher in $\text{years}$.

Find the average of all prime numbers between $60$ and $90$.

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 $\text{years}$?

The average salary of all the staff in an office of a corporate house is $Rs. 5,000$. The average salary of the officers is $Rs. 14,000$ and that of the rest is $Rs. 4,000$. If the total number of staff is $500$,what is the number of officers?