yaron235 wrote: A large collection of congruent right triangles is given, each with side length 3,4,5. Find the maximal number of such triangles you can place inside a 20x20 square, with no two triangles intersecting (in their interiors). 66?

@above This is by area. Wouldn't placement be considered?

Well 66 works. A 20*15 completely filled and a 4 5*5 with one unit square left