math is to be treated like a multidimensional array, not a continuation of numbers.
0 0123456789
1 0123456789
2 0123456789
3 0123456789
4 0123456789
--
aka

00 01 02 03 04 05 06 07 08 09
10 11 12 13 14 15 16 17 18 19
20 21 22 23 24 25 26 27 28 29
30 31 32 33 34 35 36 37 38 39
40 41 42 43 44 45 46 47 48 49

therefore taking one third of a cluster, leaves you will an inequality, and I would think, leave a remainder instead of simply being .999.... equaling 1. So to me, in my head .9999 != 1 outside of mathematical error and/or laziness. I mean, you have ten digits, it would be impossible to cut them in three ways. Where as a pie, you can. Therefore, pies are by far the most mathematically boggling, and awesome thing on this planet.