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

Question

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

 

Answer 1

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

Answer 2

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.