there is no extra one. the shapes actually doesn't really fit to a rectangle. the triangle and the rectangular prism thing both have different slopes on their gradients which are supposed to line up and make a straight line in the 13x5 configuration... so it is kind of an illusion... the extra square is squeezed between the lines!
原帖由 BiscottiGelato 於 2009-1-13 08:42 發表
Reason, (5-3)/5 =/= 3/8 (The slopes are not the same, so can't form a triagle that is supposed to constitute half the rectange. Done.