Problema Solution
The average of eleven numbers is 8. If a twelfth number
is added to these numbers, the average of all twelve
numbers is now 11. What is the twelfth number?
Answer provided by our tutors
Let 'x' represent the sum of the eleven numbers and 'y' the twelfth number.
The average of the eleven numbers is 8 means:
x/11 = 8 multiply both sides by 11
x = 8*11
x = 88
The average of all twelve numbers is 11 means:
(x + y)/12 = 11
plug x = 88 into the last equation:
(88 + y)/12 = 11
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click here to see the equation solved for y
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y = 44
The twelfth number is 44.