Solution: The Triangle Problem
This is an optical illusion. The large triangle and the smaller red and green triangles appear to be similar, but if that were the case, the tangents of their smallest angles would have to be the same.
The tangent of the green triangle is 2/5 = 0.4
The tangent of the red triangle is 3/8 = 0.375
The tangent of the whole thing is 5/13 = 0.385...
The figures are quadralaterals, and the one on the bottom is simply one unit larger.