A unit rhombus is surrounded by four congruent parallelograms. All five quadrilaterals have equal area. What are the parallelogram sides x and y?

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## Solution

The side lengths are x=1/φ and y=φ, where phi is the Golden Ratio (1+√5)/2.

First, the area of a parallelogram is sin(α) times the short side times the long side, where α is either one of the interior angles. In the diagram, this sin(α) term is the same for all parallelograms and can thus be factored out of the equations.

From equating the area of one of the outer paralellologram to the rhombus we get (y-1)y=1. It has one positive root: φ. Also, x=y-1 which is 1/φ.

## Physical solution

We are very pleased with the solution constructed by Isabel, using physical Golden triangles and gnomons.

## Poem

We were honoured to receive the following poem:

C’est le parquet ou encore le sol

Qui nous attire après nos envols

Le parquet où l’on danse

Le parquet de nos transes

Parquet en bois, ciré ou flottant,

Il est figé, immobile ou mouvant,

Le parquet est fixé sur notre terre

Qui nous protège comme une mère nourricière .