Problem 5
Show that for every integer n>=6 there exists a convex hexagon that can be dissected into exactly n congruent triangles.
Step 1 of 4: Set up congruent right-triangle blocks
Detailed analysis
Take the basic building block to be a right triangle with integer legs p and q. The official solution arranges copies into five boundary blocks L_1,L_2,M,R_1,R_2; adjoining boundaries have equal lengths, and the outer boundary is convex when the indicated combinations are used.