Four squares and five shared vertices. If the orange area is 4, what is the green area?

# Month: August 2021

## The yellow sailboat

A square, two equilateral triangles and an extended side. What is the proportion yellow : blue?

## Mondriaan II

A square contains three squares (black sides), one of which has an extended side (blue). What is the proportion yellow : blue?

## Warning triangle II

A square, a triangle and two equal angles. What is the angle α?

## The green quad

Three semicircles and a circle all touching each other. The diameters of the two smallest semicircles are given. The large triangle connects three tangency points. What is the area of the green quadrilateral?

## The strawberry ice cream

Two tangent circles and a triangle. The figure has reflection symmetry in the vertical diameter d, of which one ninth is above the horizontal chord. What fraction is pink?

## Seventies tipi II

A triangle containing two tangent semicircles. What’s the proportion α : β?

## The inner sanctum

A square with four congruent equilateral triangles. What fraction is yellow?

## The colour purple

A rectangle is split by two perpendicular lines. The four circles pass through vertices and intersection points. Their centres form a purple quadrilateral. What fraction of the large rectangle area does it cover?

## Triangle quartet II

Three coloured equilateral triangles share three vertices. Prove that the triangle formed by their centres is also equilateral.^{1}This puzzle is also known as Napoleon’s Theorem.