Question

    If the mean of five observations x, x-1, x-2, x-3, and

    x-4 is 20, then the mean of the first two observations is:
    A 23.5 Correct Answer Incorrect Answer
    B 22.5 Correct Answer Incorrect Answer
    C 21.5 Correct Answer Incorrect Answer
    D 20.5 Correct Answer Incorrect Answer

    Solution

    x, x-1, x-2, x-3, and x-4 mean of these observations – (x+x-1+ x-2+ x-3 + x-4)/5 =20 (x+x-1+ x-2+ x-3 + x-4) =100 5x-10=100 X =22. So now mean of First two observation-(22+21)/2 =21.5

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