The means of five observations is 4 and their variance is 5.2. If three of these observations are 1,2 and 6, then the other two are
(a) 2 and 9 , (b)  3 and 8 , (c) 4 and 7 , (d)  5 and 6

Options

A. 2 and 9
B. 3 and 8
C. 4 and 7
D. 5 and 6

Explanation

To solve the problem, we need to find two unknown observations \( x \) and \( y \) given that the mean of five observations is 4, and their variance is 5.2. We know three of the observations are 1, 2, and 6.

### Step 1: Calculate the sum of the observations
The mean of the observations is given by the formula:
\[ \text{Mean} = \frac{\text{Sum of observations}}{\text{Number of observations}} \]
Given that the mean is 4 and there are 5 observations, we can set up the equation:
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