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CEMC Gauss (Grade 8), 1998

Geometry Difficulty 1.0 Junior Find the answer Canada

In the circle with centre $O$ , the shaded sector represents $20\%$ of the area of the circle. What is the size of angle $AOB$ ?

(A) $36^\circ$ (B) $72^\circ$ (C) $90^\circ$ (D) $80^\circ$ (E) $70^\circ$

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