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# the average of 3 numbers is 12. If one of the numbers is 8 what are the sum of the other 2 numbers

the average of 3 numbers is 12. if one of the numbers is 8 what are the sum of the other 2 numbers i need help asap

### 2 Answers by Expert Tutors

Stephen H. | Experienced Mathematics and Computer InstructorExperienced Mathematics and Computer Ins...
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Let the variables X & Y represent the 2 missing numbers.

So, (8 + X + Y)/3 = 12

multiply both sides of the equation by 3 to get 8 + X + Y = 36

subtract 8 from both sides of the equation to get X + Y = 28

So, the sum of the 2 missing numbers is 28!

To check 8 + 28 = 36  and 36/3 = 12

Good luck!

Steve
Katherine S. | Patient Help: Math, English, Proofreading, etc. :)Patient Help: Math, English, Proofreadin...
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Since an average is a sum of numbers divided by the quantity of numbers, I would suggest working this backwards.

Average = (sum of the numbers)/quantity

So, in this case, we know that the quantity of numbers (how many there are) is 3, and we know that the average is 12.

12 = sum/3

To solve this equation, we can multiply both sides by 3.

12 (*3) = sum/3 (*3)      which leaves us with...

36 = sum of the three numbers

But we know that one of the numbers is 8, so 36 - 8 = 28.  The sum of the other 2 numbers is 28.