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The sneak peek

A rectangle with given side lengths is folded back and forth such that the corner touches the opposite side as shown. What is the minimal shaded fraction?

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Advanced

Spiegel im Spiegel

A triangle with an inscribed triangle. What fraction of the former does the latter cover in terms of lengths a, b, c, d, e and f?

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Beginner

The green necktie

A square with several line segments. What fraction is green?

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Intermediate

The red triangle

A square containing an isosceles triangle with given side lengths. What fraction is red?

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Beginner

Confined enclosure

A square containing four smaller squares. What fraction of its area is orange?

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Intermediate

The inner diamond

A triangle with side lengths a and b and an inscribed rhombus. What is the blue fraction in terms of a and b?

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Intermediate

House of the rising sun

A semicircle, a circle, a square and an equilateral triangle. The two points are the tangency point and the semicircle centre. What fraction of the total area is yellow?

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Eye of the apple

A circle with an inscribed triangle with an inscribed circle. The centre of the large circle is on the small one. What fraction of the area is blue?

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Beginner

Three squares a day

Three congruent squares inscribed in a rectangle. What fraction of the total area is green?

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Intermediate

Similar intention

A cyclic quadrilateral and two diagonals. What fraction of its area is blue?