The average of three numbers is $28$. If the first number is half of the second and the third number is twice the second,then the third number is?

$A$ man retired from his service at the age of $60$. He served for $\frac{3}{5}$ of his retirement age. At what age (in $years$) did he join his job?

The average salary of all workers in a workshop is $Rs. 12000$. The average salary of $7$ technicians is $Rs. 15000$ and the average salary of the rest is $Rs. 9000$. The total number of workers in the workshop is:

Out of four numbers,the average of the first three is $16$ and that of the last three is $15$. If the last number is $20$,then the first number is:

The average speed of a cyclist who covers the first,second,and third km at $20, 16,$ and $12 \, km/hr$ respectively (in $km/hr$) is:

The average monthly salary of $20$ employees in an organisation is $Rs. 1500$. If the manager's salary is added, then the average salary increases by $Rs. 100$. What is the manager's monthly salary (in $Rs.$)?