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

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

The average of $3$ numbers is $22$. If the first number is $\frac{3}{8}$ of the sum of the other two numbers,what is the first number?

The average of odd numbers up to $100$ is?

In an examination,the average marks were found to be $60$. The marks of $80$ candidates had to be changed from $95$ to $70$ each,and the average came down to $55$ marks. The total number of candidates who attended the examination was:

The average weight of $25$ persons is increased by $1 \, kg$ when one man weighing $60 \, kg$ is replaced by a new person. What is the weight of the new person (in $kg$)?