The ages of Grannie’s seven grandchildren are consecutive positive integers.
The youngest three grandchildren have a mean age of 6.
What is the mean age of the oldest three grandchildren?
A. 8 B. 9 C. 10 D. 11 E. 12
C. 10
Because the mean age of the three youngest grandchildren is 6, and their ages are consecutive integers, their ages are 5, 6 and 7. It follows that the ages of all the seven grandchildren are 5, 6, 7, 8, 9, 10, 11, So the ages of the three oldest grandchildren are 9, 10, 11. Hence their mean age is 10.
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