The average age of $8$ men is increased by $2\, years.$ When $2$ of them, whose ages are $20\, years$ and $24 \,years$ respectively, are replaced by $2$ women. What is the average age of these two women ? (in $years$)

The average of marks obtained by $120$ candidates in a certain examination is $35 .$ If the average marks obtained by passed candidates are $39$ and those of the failed candidates are $15,$ then what is the number of candidates who passed the examination?

The average of the first nine integral multiples of $3$ is

The average salary of the entire staff in a 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 ?

The average salary of $20$ workers in an office is $Rs. \,1900$ per $month.$ If the manager's salary is added, the average becomes $Rs. \,2000$ per $month.$ The manager's annual salary (in $Rs.$) is

In a class, there are $20$ boys whose average age is decreased by $2$ $months,$ when one boy aged $18\, years$ in replaced by a new boy. The age of the new boy is