Question 1040695
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the mean of five positive numbers is 4 when another number is added ,the mean number becomes 8. find the number added
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{{{S[5]}}} = 4*5 = 20   <--- The sum of the five numbers.

{{{S[6]}}} = 8*6 = 48   <--- The sum of the six numbers.

{{{S[6]}}} = {{{S[5]}}} + x  --->  x = {{{S[6] - S[5]}}} = 48 - 20 = 28.

<U>Answer</U>. The number 28 was added.
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Notice. The condition that the numbers are positive - is irrelevant.