SOLUTION: The mean of five numbers is 6. If one of the numbers is removed, the mean becomes 7. What is the value of the number that was removed?

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Question 316008: The mean of five numbers is 6. If one of the numbers is removed, the mean becomes 7. What is the value of the number that was removed?
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
The mean of five numbers is 6. If one of the numbers is removed, the mean becomes 7. What is the value of the number that was removed? 

Mean+=+Sum%2Fn

+6+=+Sum%2F5

30+=+Sum

Let R = the number that was removed.

Then the new Sum after removing R was 30-R

Going back to

Mean+=+Sum%2Fn

+7+=+%2830-R%29%2F4

28+=+30-R

R+=+30-28

R=2

So 2 was removed.

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Suppose the 5 numbers were 2, 5, 6, 8, 9

Their mean is %282%2B5%2B6%2B8%2B9%29%2F5=30%2F5=6

If we remove the 2, the numbers left are 5, 6, 8, 9

Their mean is %285%2B6%2B8%2B9%29%2F4+=+28%2F4+=+7

So we know we are right that 2 was removed.

Edwin