The Average of six observation is 12. The average decreases by 1 when a new observation is included. What is the seventh observation?

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Accepted Answer

Total of 6 observation = 6 x 12 = 72 Total of 7 observation (including the 7th) = 7 x (12 - 1) = 77 ∴ 7th observation = 77 - 72 = 5

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