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UKMT Intermediate Mathematical Challenge, 2016

Geometry Difficulty 2.0 Junior Find the answer United Kingdom

The diagram shows a regular octagon. What is the ratio of the area of the shaded trapezium to the area of the whole octagon?

(A) $1:4$ (B) $5:16$ (C) $1:3$ (D) $\sqrt{2}:2$ (E) $3:8$

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