New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    In a family, the mother is 3 years older than the father

    and four times as old as the son. If the sum of their present ages is 90 years, how many years later will the father be twice as old as the son?
    A 25 yrs Correct Answer Incorrect Answer
    B 20 yrs Correct Answer Incorrect Answer
    C 17 yrs Correct Answer Incorrect Answer
    D 18 yrs Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the present age of the son and the mother be 'x' years and '4x' years, respectively.

    Then, present age of the father = (4x - 3) years

    So, x + 4x + (4x - 3) = 90

    Or, 9x - 3 = 90

    So, x = (90 + 3) ÷ 9 = 10

    Present ages of the son and father are 10 years and 37 years, respectively.

    For some 'y',

    (10 + y) × 2 = (37 + y)

    Or, 20 + 2y = 37 + y

    So, y = 17

    17 years hence from now, the father will be twice as old as the son.

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