Three numbers have a mean of 8. If we add a 4th number, the mean is now 7. What number was added?

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Answer 1 · 2017-12-16T09:24:34

#x=4#

The mean is the sum of the values divided by the count. In the first part of this, we have 3 numbers with a mean of 8:

#"sum"/3=8#

#"sum"=24#

In the second part, we have the 3 numbers plus #x# with a mean of 7. What is #x#:

#(24+x)/4=7#

#24+x=28#

#x=4#