This:

Has puzzled me long enough, to try and figure it out. If you simply (print the lot and) cut the pieces on the top figure, and compare them to them to those on the bottom figure, you may find they are identical, thus adding to the mystery.
However, "Near Fly-By" was suggested, and argued that the dark green (5 x 2) and the red triangles (8 x 3) are not identical in their corresponding angles, making their common, continuous hypotenuse, not a straight line but two, thus making the general figure a rectangle rather than a triangle, with the difference in area to explain the obvious oddity, as follows:

Can any one suggest a more elegant explanation ?
"Almost" Good Answers: