Willsfords arithmetick, naturall, and artificiall: or, decimalls. Containing the science of numbers, digested in three books. Made compendious and facile for all ingenious capacities, viz: merchants, citizens, sea-men, accomptants, &c. Together with the theorie and practice united in a sympathetical proportion betwixt lines and numbers, in their quantitites and qualities, as in respect of form, figure, magnitude and affection: demonstrated by geometrie, illustrated by calculations, and confirmed with variety of examples in every species. / By Thomas Willsford, Gent.

Question 3. If a mans 3 Sonnes spent 57 L. in 4 moneths, what would his 5 sonnes expences have been at that rate in the space of 12 moneths?

The first question I have

	S.	L.	S.
1 Rule.	3	57	5
	M.		M.
2 Rule.	4		12
Prod.	12	57	60
Or as	1	57	5
Facit		285 L.

here stated again, to satisfie the Reader, in the operation of this double Rule at one worke, by a single Rule of Three at most, if not reduc'd unto a Rule of Practice, as in this Example; where in the first Rule stands 3 S. 57 L. & 5 S. In the second Rule is placed for the two extremes the time, viz: 4 M. & 12 M. the demand is of the 5 S. and the 12 M. The other 3 numbers were proposed, viz: 3 S. 57 L. 4 M. if 57 L. were multiplied by 5 and divided by 3, the Quotient would be 95 for the fourth number, and a meane proportionall in the

second Rule, and that multiplied by 12 and divided by 4 will solve the Question: then for brevity, since the number or summe here required is contained in 57 L. twice multiplied, and as often divided, I say if the two Multipliers, multiplied into one Multiplier, and the two Dividers into one Divider, the propor∣tions must be the same; therefore by the 14 Axiome this Example with two Rules will be reduc'd to one, the product of the Multipliers is 60, and the Divi∣sors 12, so the proportion is as 12 to 57 L. so 60 to 285 L. or reduced by the Rule of Practice, as 1 to 57 L. so 12 will be in proportion unto 285 L. as before, the Question solved.