': 



RULE. 



by 3 yards, quotes 40s. without a remain- 

 der : so 40s. or "21. is the number sought. 

 Quest. 2. If 4/6. of sugar cost 2s. 9</. 

 what is the value of 18/6. ? Answer 12s. 

 4|d 



Work. 

 lb. s. d. Ib. 

 42 : 9 J8 

 12 



33 d. 

 18 



264 



4)594(148rf. 

 2 

 4 



Explanation. The supposition is in 4/6. 

 and 2s. 9</. this last term being liice the 

 thing sought, which is connected with 

 18/6. wherefore the terms are stated ac- 

 cording to the rule : then the middle term 

 being mixed, it is to be reduced to pence ; 

 and then argue thus; if 4 lb. cost 33tf., 

 18 lb must cost more ; therefore multiply 

 33.'/. by 18/6. and divide their product by 

 4 ; the quotient is 14.3d. and 2 remains, 

 which is to be reduced to farthings, and 

 the product, divided by the former quo- 

 tient, gives 2; so the answer is l48r/. 2 

 farthings, or 12s. 4$d. because H&/. is, 

 by reduction, 12s. 4</. 



Quest. 3. What time will 7 men be 

 boarded for 25/. when 3 men paid 251. for 

 6 months? Answ. 2 months, 16 days, rec- 

 koning 28 days to 1 month. 



Work. 

 men. months, men. 



3 



7)18(2 

 14 



Rem. 4 



28 



7)112(16 days. 



' Explanation. The 257. is a superflu- 

 ous number ; then the supposition is in 

 the 3 men and 6 months, and the de- 

 mand regards the 7 men : the terms be- 

 ing all simple, you are to argue thus ; if 

 3 men are boarded 6 months for 25/. (or 

 any sum), 7 men will be boarded for the 

 same a shorter time : therefore multiply 



6 months by 3, and divide the product 

 18 by 7, whereby the answer is found to 

 be 2 months and 16 days. 



Note. The first two questions are what 

 is called the rule of three direct, that is, 

 where the third term, being greater or 

 less than the first, requires that the An- 

 swer also be greater or lesser than the 

 second term. The last, of the rule of 

 three indirect, or reverse; where the third 

 term, being greater or lesser than the first, 

 requires the fourth contrarily lesser or 

 greater than the second. But we have com- 

 prehended both in one general rule. And 

 from this observation mav be learned what 

 questions are of either kind. 



ROLE, or RUIER, an instrument of 

 wood or metal, with several lines deline- 

 ated on it, of greai use in practical men- 

 suration. When a ruler has the lines of 

 chords, tangents, sines, &c. it is called a 

 plane scale. 



The carpenter's joint rule is an instru- 

 ment usually of box, &c. twenty-four 

 inches long, "and one and a half broad ; 

 each inch being subdivided into eight 

 parts. On the same side with these cli- 

 visions is usually added Gunter's line of 

 numbers. On the other side are the lines 

 of timber and board measure; the first be- 

 ginning at 82, and continued to 36, near 

 the other end ; the latter is numbered 

 from 7 to 36, 4 inches from the other end. 

 W T e shall point out some of the uses of 

 this rule. 



The application of the inches, in mea- 

 suring lengths, breadths, &c. is obvious. 

 Tha^of the Gunter's line, see under the 

 article GUTTER'S LINE. 



The use of the other side is that with 

 which we are now concerned. 1. The 

 breadth of any surface, as board, glass, 

 &c. being given, to find how much in 

 length makes a square foot. Find the 

 number of inches the surface is broad, in 

 the line of board measure, and right 

 against it is the number of inches requir- 

 ed. Thus, if the surface were eight inch- 

 es broad, eighteen inches will be found 

 to make a superficial foot. Or more rea- 

 dily thus: apply the rule to the breadth 

 of "the board, or glass, that end, marked 

 36, being equal with the edge, the other, 

 edge of the surface will show the inches, 

 and quarters of inches, which go to a 

 square foot. 2. Use of the tuble at the 

 end of the board-measure. If a surface 

 be one inch broad, how many inches long 

 will make a superficial foot ? look in the 

 upper row of figures for one inch, and 

 under it in the second row is twelve 

 inches, the answer to the question. 3i 



