From ALAN BLAIRM
That the ratio of the diameter to the circumference of a circle, designated
as pi, is about 3 has been known since antiquity (Letters, 26 October, 9
and 23 November); in fact, as noted by John Fauvel (9 November), a value
of 3 for pi appears in the Old Testament (I Kings vii, 23; II Chronicles
iv, 2). The Greeks used a more accurate value of 221 7 (error 0-04 per cent);
and the Egyptians used a ratio of two squares: 256/81 (error 0.6 per cent).
A simple way of obtaining an accurate value for pi is to write each of the
first three odd numbers twice, and divide the second half by the first,
355/113 (error 0.085 parts per million).
may also remember the mnemonic ‘How I wish I could calculate pi easily
quite fast’, and write down the number of letters in each word.
Alan Blair Julich, Germany
