These are the ages of the members of Dion's swim team. The mean age is 10.
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Answer: The mean of the list given is 10.
To find the mean of a list of numbers, first add up all the numbers.
10 + 10 + 11 + 9 = 40
Now, divide the list by the total number of people.
40 / 4 = 10
The mean of this list is 10.