The average salary per head of all the workers in a workshop is $Rs. 850$. If the average salary per head of $7$ technicians is $Rs. 1000$ and the average salary per head of the rest is $Rs. 780$,find out the total number of workers in the workshop.

The average daily wages of $A, B$ and $C$ is $Rs. 120$. If $B$ earns $Rs. 40$ more than $C$ per day and $A$ earns double of what $C$ earns per day,the wages of $A$ per day is (in $Rs.$)

The arithmetic mean of the scores of a group of students in a test was $52$. The brightest $20\%$ of them secured a mean score of $80$ and the dullest $25\%$ a mean score of $31$. The mean score of the remaining $55\%$ is

The average age of a board of directors of a company,having $10$ directors,was $48$ years. Coincidentally,when a director aged $53$ resigned from the board,another director died on the same day. $A$ new director aged $34$ joined the board. Next year in the same month,the average age of all the $9$ directors was found to be $46$ years. The age of the late (i.e.,dead) director at the time of his death was (in years):

The average of $50$ numbers is $30.$ If two numbers,$35$ and $40$ are discarded,then the average of the remaining numbers is nearly.

The average marks of students in an examination was $65$. It was later found that the marks of one student had been wrongly entered as $83$ instead of $38$. If there were $50$ students, what is the correct average?