The Double Rule of Three, tfc.         135

(3)  If 3£ yards of cloth, that is l-f yard wide, be sufficient to make a cloak—how much must I have of that sort which is y yard wide, to make another of the same size ?

Ans. 4§ yards.

(4)  If 8 men can do a piece of work in 4£ hours—in how many hours will 10 men do the same work ?

Ans. 1-j-g hours.

(5)  If a penny white loaf weighs 7 oz. when a bushel of wheat costs 5s. 6d.—what  is the bushel  worth  when   the penny white loaf weighs but 2J oz. ?                Ans. 15*. A*d.

(6)  What quantity of shaloon that is J yard wide will line 7-J yards of cloth that is l£ yards wide ?

Ans. 15 yards.

THE DOUBLE RULE OF THREE

IN VULGAR FRACTIONS.

EXAMPLES.

(1)  If a carrier receives £2-[% for the carriage of 3 cwt. 150 miles—how much ought he to   receive for  the carriage of 7 cwt. 3£ qrs. 50 miles?

Ans. £] : 16 : 0.

(2)  If £100. in 12 months gain £6. interest—what principal will gain £3J in 9 months?                                 Ans. 75.

(3)  If 9 students spend JClOi in  18 days—how much will ',20 students spend in 30 days ?

Ans. £39 : 18 : 4-^.

(4)  A man and his wife having laboured 1 day earned 4§s. '—how much must they have for 10 j days when their 2 sons helped them ? .                                          Ans. £4 : 17 : 1£.

(5)  If £50. in 6 months gain £2-^—what time will £\o% require to gain JBl-rr?

Ans. 9 month*.

(6)  If the carriage of 60cwt.  20 miles cost £\4%—what weight can I have carried 30 miles for £5T7^?

Ans. 15 act.