Page:Curious Myths of the Middle Ages (1866).pdf/222

 tician. The property to which I allude is this, that when 9 is multiplied by 2, by 3, by 4, by 5, by 6, &c., it will be found that the digits composing the product, when added together, give 9. Thus:

It will be noticed that 9 × 11 makes 99, the sum of the digits of which is 18 and not 9, but the sum of the digits 1 + 8 equals 9.

And so on to any extent.

M. de Maivan discovered another singular property of the same number. If the order of the digits expressing a number be changed, and this number be subtracted from the former, the remainder will be 9 or a multiple of 9, and, being a multiple, the sum of its digits will be 9.

For instance, take the number 21, reverse the digits, and you have 12; subtract 12 from 21, and