The average of a non-zero number and its square is $5$ times the number. The number is

$A$ batch of $60$ students made an average score of $50$ marks and another batch of $40$ students made an average score of $45$ marks. What is the overall average score?

The average age of a family of $6$ members $4$ years ago was $25$ years. Meanwhile,a child was born in this family,and the average age of the whole family is still the same today. The present age of the child in years is?

The average weight of $3$ men $A, B$ and $C$ is $84 \, kg$. Another man,$D$,joins the group,and the average weight 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 weight of $3$ men $A, B,$ and $C$ is $84 \, kg$. Another man $D$ joins the group and the average weight 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 $A$ in $kg$ is:

The average of first three numbers is double of the fourth number. If the average of all the four numbers is $12,$ find the $4^{th}$ number.