Augustus De Morgan,
Elements of arithmetic
(1858)
“ Multiply the numerator by the whole number, and let the denominator remain.117. If the denominator of the fraction be divisible by the whole number, the rule may be stated thus: Divide the denominator of the fraction by the whole number, and let the numerator remain. For example, multiply 7/36 by 6. This (116) is 42/36, which, since the numerator and denominator are now divisible by 6, is (108) the same as 7/6. It is plain that 7/6 is made from 7/36 in the manner stated in the rule.118. Multiplication has been defined to be the taking as many of one number as there are units in another. ”
