Question
The ratio of the present ages of a son and his father
3:7 and that of his mother and father is 6:7. Four years ago, the ratio of the age of the son that of his mother becomes 1:4. What is the age of the son?Solution
The ratio of the present ages of a son and his father = 3:7 His mother and father = 6:7 Father : Mother = 7:6 Son : Father = 3:7 Son : Father : Mother = 3:7:6 4 years ago, Son : mother = 1:4 Let the age of son = 3x Father = 7x Mother = 6x `(3x-4)/(6x-4)` = `1/4` 12x - 16 = 6x- 4 12x- 6x = - 4 +16 6x = 12 x = 2 Present age of son = 3 × 2 = 6 years
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