A square containing two overlapping equilateral triangles. What’s the length proportion a : b?
Seeing double
Five circles, of which the green circles are congruent and so are the blue ones. If rblue : rgreen= 6, what’s rred : rgreen?
Égalité
A square with its diagonal and a circle. If red is equal to blue, what’s the angle α?
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?
The lever of Archimedes
Two congruent triangles are placed as shown. A line segment passes through the centroid of the yellow triangle. What’s the proportion a : b?
The green necktie
A square with several line segments. What fraction is green?
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?
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?
Head above water
A unit square with an extended side immersed in another square. What is the area of the red triangle?
The framing effect
Four squares, three of which are coloured. What’s the area of the blue one?