The inner diamond

A triangle with side lengths a and b and an inscribed rhombus. What is the blue fraction in terms of a and b?

Scroll down for a solution to this problem.


The blue fraction is 2ab/(a+b)2.

Solution by Matthew Arcus.

The top triangles are similar to the whole, and are in proportion a:b, so their area (as a fraction of the whole) is A = (a²+b²)/(a+b)², so blue area is 1-A = 2ab/(a+b)².


The inner diamond
The brightness of a diamond
Cannot be seen
Shining from inside
You must search it to find
No precious stone can materialize
To be a real good human being
Inner beauty shines from the heart
It is not a merchandise
And has
As much value as a rubie


🤞 Don’t miss these puzzles!

Subscribe to the weekly geometry puzzle e-mail.

Leave a Reply

Your email address will not be published. Required fields are marked *

Optionally add an image (JPEG only)