Four squares. The red vertex is the centroid of the red triangle. What is the yellow area?
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Four square
Category: Intermediate
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Connected centres
Two quarter circles and a semicircle. The blue points are quarter and semicircle centres. What is red : green?
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Euclid’s wing
Several line segments, some of which are parallel. What is green : orange?
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Dancing squares
Four squares and one centre. Prove that the red quadrilateral is a parallelogram.
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Making a dent
A right triangle with one trisected angle. What’s the angle α?
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The tetromino
A square, its diagonal and six smaller squares. What fraction is purple?
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The pumpkin
A regular hexagon and a circle centred in the blue point. What’s the angle α?
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Crazy hat
The diameter of the semicircle is a side of a rectangle. Show that for any such rectangle, and any point along its top edge, the configuration produces three collinear red dots.
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Bottoming out
Two squares and a circle. What’s the angle α?
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The tipi entrance
A semicircle with three tangents. Prove that purple : green = red : yellow.