$A$ batsman in his $17^{th}$ innings makes a score of $85$ runs,and thereby,increases his average by $3$ runs. What is his average after the $17^{th}$ innings? He had never been 'not out'.

The average temperature from Monday to Thursday is $48^{\circ} C$ and from Tuesday to Friday,the average temperature is $52^{\circ} C$. If the temperature on Monday is $42^{\circ} C$,what was the temperature on Friday in $^{\circ} C$?

The average weight of a group of $20$ boys was calculated to be $89.4 \, kg$ and it was later discovered that one weight was misread as $78 \, kg$ instead of $87 \, kg$. The correct average weight is (in $kg$).

Average rainfall on Monday,Tuesday,Wednesday and Thursday is $420.5\, cm$ and average on Tuesday,Wednesday,Thursday and Friday is $440.5\, cm$. If the ratio of rainfall for Monday and Friday is $20:21$,find the rainfall in $cm$ on Monday and Friday.

The average of the test scores of a class of $m$ students is $70$ and that of $n$ students is $91$. When the scores of both the classes are combined,the average is $80$. What is $n / m$?

$A$ club has $15$ men and $25$ women. The average age of men is $10 \text{ years}$ and the average age of women is $12 \text{ years}$. What is the average age of the whole club in years?