Where did it go?

Hehe a classic..I'll try to find the link that has an explanation for this problem..

Here is the explanation; (please click the highlighted place below)

http://72.14.221.104/search?q=cache:5mXpMkV5GX0J:www.exn.ca/Stories/2000/05/1

[color=red]"From where comes this 'hole' ?" [/color]

Shouldn't it be something like: "Where does this h

The hypotenuse is 13 cells long and 5 high.5/13 is an irreducible fraction.
Therefore, the hypotenuse never crosses the grid's nodes except for its two ends. Thus, the trick is based on an optical deception: the defect is so little that you just don't see it. But it can be easily calculated.

EDIT: Note, that the hypotenuses on the two drawings are different. And neither is a straght

smart

A simple (rather dumb) answer would be: the square was forgotten to be coloured!