The picture of the rectangle is deceptive!
The line XY shown in the picture of the rectangle (see below)
is not a line at all. The parts XU and VY have a gradient
of 2 / 5 = 0.4, and the parts XV and UY have a gradient of
3 / 8 = 0.375. So, in fact, XUYV is a parallellogram with an
area of 1, not a line!
Two versions of this riddle are published on this site.
It can also be found under:
Appearing Area.