Question

In a joint family of seven members, the average age of grandparents is $65$ years, that of parents is $34$ years and that of three children is $4$ years. Find the average age of the family.

Answer 1

$\Rightarrow$ Average age of grandparents is $65years$

$\therefore$ Sum of grandparents age $=65\times 2=130years$

$\Rightarrow$ Average age of parents is $34years$

$\therefore$ Sum of parents age $=34\times 2=68years$

$\Rightarrow$ Average age of $3$ children $=4years$

$\therefore$ Sum of children age $=3\times 4=12years$

$\Rightarrow$ Average age of family $=\frac{130+68+12}{7}$

$=\frac{210}{7}$

$=30years$