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    Question

    The average of 10 numbers is 21.6. The average of the

    first four numbers is 17.5, and the average of the last three numbers is 24. The fifth number is 6 less than the sixth number, which itself is 8 less than the seventh number. What is the average of the fifth and sixth numbers?
    A 21 Correct Answer Incorrect Answer
    B 25 Correct Answer Incorrect Answer
    C 28 Correct Answer Incorrect Answer
    D 19 Correct Answer Incorrect Answer
    E 24 Correct Answer Incorrect Answer

    Solution

    Sum of fifth, sixth and seventh numbers = 21.6 X 10 - 17.5 X 4 - 24 X 3= 216 - 70 - 72 = 74Let the seventh number be 'p'.Sixth number = p - 8Fifth number = p - 8 - 6 = p - 14So, p + p - 8 + p - 14 = 74Or, 3p - 22 = 74Or, 3p = 96Or, 'p' = 32Required average = (p - 8 + p - 14) ÷ 2 = p - 11 = 32 - 11 = 21

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