Categories
Beginner

Three folds

A square divided by three line segments. What’s the proportion yellow : purple?

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Intermediate

Égalité

A square with its diagonal and a circle. If red is equal to blue, what’s the angle α?

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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?

Categories
Beginner

The green necktie

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

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Intermediate

House of Orange

A right triangle with a red and yellow square attached. Two circular arcs centered in the triangle vertices. What is the area of the orange rectangle in terms of red and yellow?

Categories
Advanced

Out of proportion

An equilateral triangle containing a parallelogram, another equilateral triangle and a circular arc that is tangent in its base vertices. What is the proportion pink : blue?

Categories
Intermediate

Head above water

A unit square with an extended side immersed in another square. What is the area of the red triangle?

Categories
Intermediate

The framing effect

Four squares, three of which are coloured. What’s the area of the blue one?

Categories
Beginner

Projection bias

Two regular pentagons are placed side by side. What’s the proportion blue : green?

Categories
Intermediate

Take five origami

Divide a rectangular piece of paper in five pieces of equal area. You only have a pair of scissors at your disposal, but you are allowed to make straight folds to guide you.