Question

In a family of 6 members, the average age of the family at present is 25 while the age of the youngest member in the family is 5yrs, so what will be the average age of the family at the time of his birth ?

Answer 1

Average age of $6$ family member is $25$.

$\therefore$ Total age of $6$ family member $=6\times 25=150years$

The age of youngest member is $5years$

$\Rightarrow$ Total age of $6$ family member at the times of youngest birth $=150-(5\times 6)$

$=150-30$

$=120years$

$\therefore$ Average age of family at time of youngest birth $=\frac{120}{6}=20years$