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?

The average weight of $3$ men $A, B$ and $C$ is $84 \, kg$. Another man $D$ joins the group and the average now becomes $80 \, kg$. If another man $E$,whose weight is $3 \, kg$ more than that of $D$,replaces $A$,then the average weight of $B, C, D$ and $E$ becomes $79 \, kg$. The weight of $A$ is (in $kg$)

The average score of Sachin after $25$ innings is $46$ runs per innings. If after the $26^{th}$ innings,his average runs increased by $2$ runs,then what is his score in the $26^{th}$ innings?

The average of nine numbers is $50$. The average of the first five numbers is $54$ and that of the last three numbers is $52$. Then the sixth number is?

If the average of $m$ numbers is $n^{2}$ and that of $n$ numbers is $m^{2},$ then the average of $(m + n)$ numbers is

$A$ man whose bowling average is $12.4$ takes $5$ wickets for $26$ runs and,thereby,decreases his average by $0.4$. The number of wickets taken by him before his last match is: