Question
18 years ago the average age of a family of four
members was 45 years. Two children were born in that span of 18 years. The present average age of the family remained unchanged. Among the two children who were born in between the 18 years, if the older child at present is 12 years more than the younger one, what is the respective ratio between the present age of the older child and the present age of the younger child?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 Hence the required ratio = (3+12) : 3                        = 15: 3 = 5: 1
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