.Mzcw.NzE2NA

(3) 40. Some authors use a particular notation for arithmetical proportion For instance, if the quantities: a, b, c, & d be in arithmetical proportion they express unclear or thus, a. b:. c,, d. But this is unclear a - b = c - d, or b - a = d - c expressed unclear Arithmetical proportion perfectly well.

49. In every proportion the first & last quantities or terms, are called underline extreems, /underline the others are called underline means. /underline

50. In every arithmetical proportion the sum of the means is equal to the sum of the extreems. Thus if, a, b, c, d, be in arithmetical proportion, unclear that a + b = b + c. For by the supposition,

formula 2. D. b.