$A$ cricketer had a certain average of runs for his $64$ innings. In his $65^{th}$ innings,he is bowled out for no score on his part. This brings down his average by $2$ runs. What is his new average of runs?

The average of $5$ consecutive integers starting with $m$ is $n$. What is the average of $6$ consecutive integers starting with $(m + 2)$?

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

$A$ person covers $9 \, km$ with a speed of $3 \, km/h$,$25 \, km$ with a speed of $5 \, km/h$,and $30 \, km$ with a speed of $10 \, km/h$. Find the average speed of the person in $km/h$.

The average revenue of $13$ consecutive years of a company is $Rs. 70$ lakhs. If the average of the first $7$ years is $Rs. 65$ lakhs and that of the last $7$ years is $Rs. 77$ lakhs,find the revenue for the $7^{th}$ year (in $Rs.$ lakhs).

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?