Two squares share a vertex. Prove that the red point is the circumcentre of the red triangle.
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Stay centred
Category: Beginner
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Peeping out
A unit square and a rectangle. What is the blue area?
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Pythagoras times three
Three squares on a grid. What is the ratio of the areas red : green : purple?
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Bandaged head
A regular decagon and triangles from vertices and side midpoints. What fraction is red?
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Between the lines II
Two rectangles are at right angles and have equal area. Prove that the three black lines are parallel.
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The heptagon square
What is the angle α between the blue line and the baseline of the orange square?
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A golden year
Two squares, a rectangle and a semicircle. What is yellow : green?
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Decorating the tree
A symmetric tree has decorative lines of equal slope, and of lengths 11 and 13. What is the area ratio of green to red to brown?
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The brick pile
Three congruent rectangles inscribed in a triangle. What fraction is brown?
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Inside the box
Two squares inside a square share a vertex. What’s the angle α?