(2) Let the number of males in thesociety be x and the number of femalesbe y. Sum of the ages of males in thesociety = 21x yrs. Sum of the ages of females in thesociety = 18y yrs. Average age of people in the society= 20 ∴
21x+18y
x+y
=20 ⇒21x + 18y = 20(x + y) ⇒21x + 18y = 20x + 20y ⇒21x – 20x = 20y – 18y ⇒x = 2y ⇒x/y=2/1 ∴ Ratio of the number of males tothe number of females is 2 : 1.