As I mentioned in a blog entry last week, the value of pi slips away from you if you try to state it as a simple fraction, even in a good try such as 22/7. If we represent numbers in decimal rather than fractional form we can express the strangeness of pi, its irrationality, in a different way. We can turn any simple fraction into one of three sorts of number: a simple integer, an integer followed by a string of decimals that comes to a definite end, or an integer followed by the string of decimals that doesn’t come to an end but that settles down into satisfyingly dull repetition. Here are some simple fractions: 9/3, 11/4, and the aforementioned 22/7. The first, 9/3, resolves itself into the integer 3. 11/4 is 2 ¾, or in decimal form 2.75. That is where it terminates. 22/7 is 3 1/7 or in decimal form 3.142857142857.... It is a repeating decimal. That is: the sequence "142857" will continue repeating for as long as you have the patience to ...