$A$ man whose bowling average is $12.4$ takes $5$ wickets for $26$ runs and,thereby,decreases his average by $0.4$. The number of wickets taken by him before his last match is:

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

The average of five numbers is $27$. If one number is excluded,the average becomes $25$. The excluded number is

The average of the first $25$ numbers is $10$ and the average of the next $25$ numbers is $12$. The average of all $50$ numbers is:

The average age of four brothers is $12 \, \text{years}$. If the age of their mother is also included, the average increases by $5 \, \text{years}$. The age of the mother (in $\text{years}$) is:

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?