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Five observations with mean 24/5 and variance 194/25, first four have mean 7/2: variance of the first four

The same question, asked 2 times: 29 Jun 2022*, 29 Jan 2024. Every wording below, oldest first.

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  1. Question 1

    29 Jun 2022

    80
    Let the mean and the variance of 5 observations x1,x2,x3,x4,x5x_{1},x_{2},x_{3},x_{4},x_{5} be 245\frac{24}{5} and 19425\frac{194}{25} respectively. If the mean and variance of the first 4 observation are 72\frac{7}{2} and aa respectively, then (4a+x5)\left( 4a +x_{5} \right) is equal to:

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  2. Question 2

    29 Jan 2024

    154
    If the mean and variance of five observations are 245\frac{24}{5} and 19425\frac{194}{25} respectively and the mean of first four observations is 72\frac{7}{2}, then the variance of the first four observations is equal to

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