Three squares are placed in a row. Prove that the red vertices are collinear.
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A dangerous step
Category: Beginner
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Projection bias
Two regular pentagons are placed side by side. What’s the proportion blue : green?
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The voting pencil
A square and a rectangle share a vertex. Two triangle areas are given. What is the total area?
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The pentagon attack
Two regular pentagons and two diagonals. What’s the angle α?
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Confined enclosure
A square containing four smaller squares. What fraction of its area is orange?
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Lean on me
Two squares and two diagonals. Prove that the angles α and β are equal.
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The dolphin
Two semicircles, a tangent and an altitude to the tangency point. Prove that the red triangle is isosceles.
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Parallelism
A trapezium with its diagonals and a parallel line segment. What’s the proportion blue : red?
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The Common Brimstone
A square divided by three line segments. What’s the proportion green : yellow?
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Tension control
Three squares and a line segment of which a vertex is the midpoint. What is the proportion purple : green?