Answer: 26 (choice C)
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Step-by-step explanation:
The mean of all ten numbers is 22.
This tells us the sum of those ten numbers is 10*22 = 220
Recall that
mean = (sum of items)/(number of items)
We take this process in reverse to find the sum.
In other words:
sum = (mean)*(number of items)
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Now remove the elements {8,12,21,23} to get a new sum of:
220-8-12-21-23 = 156
Divide that smaller sum over 6 since removing 4 elements leaves us with 10-4 = 6 left over.
new mean = (new smaller sum)/(number of items)
new mean = (156)/(6)
new mean = 26