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    Question

    Find the fourth proportion of (3k + 3), (6k + 6) and

    (9k + 9). (Note: 'k' is the largest single-digit composite number.)
    A 120 Correct Answer Incorrect Answer
    B 150 Correct Answer Incorrect Answer
    C 160 Correct Answer Incorrect Answer
    D 180 Correct Answer Incorrect Answer

    Solution

    'k' = 9 3k + 3 = 3 × 9 + 3 = 30 6k + 6 = 6 × 9 + 6 = 60 9k + 9 = 9 × 9 + 9 = 90 Let the fourth proportion be 'm'. 30 : 60 :: 90 : m So, 30 × m = 60 × 90 Or, 'm' = 180

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