18 years ago the average age of a family of four members

Solution

18 years ago, The sum of age of a family of four members = 45 × 4 = 180 years Now at present,  The sum of age of four members = 180 + 18 × 4 =252 years Let the Present age of younger child be x years And the present age of older child = (x + 12) years Now, as per the question 252 + x + 12 + x = 45 × 6 2x = 270 – 264 2x = 6 x = 3 Present age of the older child = x + 12 = 3 + 12 = 15 years Present age of the younger child = x = 3 years Respective ratio = 15 : 3 = 5:1