Ok - It was buggin the crap out of me so I figured it out -- referring to the triangle thing.
Since I don't have pictures, I will refer to individual shapes by their colors, the top composite as A and the bottom as B.
The total area of both A and B is the same: 32 units. The problem is that the pictures are an optical illusion (with the aid of thick lines.)
The slope of the green triangle is .4 and the slope of the red is .375. Therefore, while it looks like the hypotenuese of the composite is one straight line, it is actually two straight lines, angling slightly in the middle. You can tell because the added length of the hypoteneuse of green and red equals 14.045, while the length of the hypoteneuse of a 5x13 triangle should be 13.928.
Composite A bows slightly in - the red triangle has less of a slope than the green.
Composite B bows slightly out. This bow (along with the excessively thick lines) give the composite enough extra room to shove that "hole" in.
If none of that stuff made sense, just remember that the composites are not true triangles - and that A and B are not exactly the same shape. (though they look like it.)
IB Trigonometry finally pays off!