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Question
If the mean of five observations x, x + 2, x + 4, x + 6, x + 8, is 11, then the mean of first three observations is
Options
9
11
13
15
Solution
9
Explanation;
Hint:
Mean = `(x + x + 2 + x + 4 + x + 6 + x + 8)/5`
11 = `(5x + 20)/5`
5x + 20 = 55
5x = 55 – 20
= 35
x = `35/5`
= 7
Mean of first 3 observation is = `(7 + 9 + 11)/3`
= 9
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