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UKMT Grey Kangaroo, 2022

Algebra Difficulty 2.0 Junior Find the answer United Kingdom

Three sisters, whose average age is 10, all have different ages. The average age of one pair of the sisters is 11, while the average age of a different pair is 12. What is the age of the eldest sister?

(A) $10$ (B) $11$ (C) $12$ (D) $14$ (E) $16$

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