(idea) by /dev/joe Thu May 18 2000 at 17:52:29
An old chestnut goes like this:

There are a few variations of this, but the most common today seems to work like this. 

                      __---|
                 __---     | 3
            __---          |
       __--+---------+-----+
  __---    |   +-+---+     | 2
 ----------+---+-+---------+
      5      2  1      5

Split the above (crude ASCII drawing, sorry) of a 13x5 right triangle into five pieces as shown. Then rearrange the largest four as shown below: 

                      __---|
                 __---     | 2
            __---+---------+ ,__ 1
       __---     |   +-----+ `
  __---          +---+     | 2
 ----------------+---------+
         8             5

We've got the whole 13x5 right triangle again -- but we didn't use the little square? Where did the little square go?

Answer

I like it!