Animation of <a href="https://en.wikipedia.org/wiki/Missing_square_puzzle" class="extiw" title="w:Missing square puzzle">Missing square puzzle</a>. The hole results because the two triangle pieces do not have the same ratio: the blue triangle is 2:5, while the red triangle is 3:8. The initial shape of the complete puzzle is not a triangle, but a quadrilateral, since what appears to be the hypotenuse is actually bent.
<a href="https://en.wikipedia.org/wiki/User:Trekky0623" class="extiw" title="wikipedia:User:Trekky0623">Trekky0623</a> at <a href="https://en.wikipedia.org/wiki/" class="extiw" title="wikipedia:">English Wikipedia</a>
<a class="external free" href="https://commons.wikimedia.org/wiki/File:Missing_Square_Animation.gif">https://commons.wikimedia.org/wiki/File:Missing_Square_Animation.gif</a>