Wei-Hwa Huang sent this puzzle. "Divide a square into 7 triangles. One triangle must have edge lengths in the ratio 3:4:5. The other 6 triangles must be arrangeable into another square!" He asks if the same task can be done with less than seven triangles.
Wei-Hwa Huang's Pythagorean challenge has at least 4 solutions with 7 triangles. These were found by Wei-Hwa Huang, Junk Kato, Andrew Cook, and Livio Zucca.