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    Question

    Four years ago, the ages of the father and his son were

    in the ratio 7:2. Four years hence, the ages of the father and his son will be in the ratio 9:4. After how many years will the father's age be twice the age of his son?
    A 12 Correct Answer Incorrect Answer
    B 8 Correct Answer Incorrect Answer
    C 10 Correct Answer Incorrect Answer
    D 9 Correct Answer Incorrect Answer

    Solution

    Let the common ratio be x. Hence, four years ago, the ages of the father and his son were 7x and 2x years. According to the question, (7x+4+4)/ (2x + 4 + 4) = 9:4 28x+ 32 = 18x + 72 10x = 40 x=4 Present age Father = 7x + 4 = 7 x 4 + 4 = 32 Son = 2x + 4 = 2 x 4 + 4 = 12 After P years the father's age will be twice the age of his son. According to the question, 32 + P = 2 x (12 + P) P = 8 year

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