The average age of $5$ boys is $16$ years, of which the average age of $4$ boys is $16$ years $3$ months. The age of the $5^{th}$ boy is:

The average age of $24$ boys and their teacher is $15 \text{ years}$. When the teacher's age is excluded,the average age decreases by $1 \text{ year}$. What is the age of the teacher in years?

$A$ batsman scores $98$ runs in the $17^{\text{th}}$ match of his career. His average runs per match increases by $2.5$. What is his average before the $17^{\text{th}}$ match?

$5$ members of a team are weighed consecutively and their average weight is calculated after each member is weighed. If the average weight increases by $1 \ kg$ each time,how much heavier is the last player than the first one? (in $kg$)

The average marks obtained by $40$ students of a class is $86$. If the $5$ highest marks are removed,the average reduces by $1$ mark. The average marks of the top $5$ students is

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.