Supplement to the Double Hule of Three. QUESTIONS. 1. WHAT is the Double Rule of Three; or COMPOUND PROPORTION? 2. How are questions to be stated in the Double Rule of Three ? 3. How is it known, after the statement of the queftion, whether the pro portion be direct or inverfe? 4. When the proportion is Direct, how is the answer to be found? 5. When the proportion is Inverfe, how is the answer to be found?. EXERCISES. 1. If 6 men build a wall 20 feet long, 6 feet high, and 4 feet wide in 16 days, in what time will 24 men build one 200 feet long, 8 feet high and 6 thick? Ans. 80 days. The folid contents in each piece of wall, ac, cording to the given dimenfions, must be found before stating the quef tion. 2. If the freight of 12Cwt. 2qrs. 6lb. 275 miles, coft $27,78; how far may 60cwt. 3qrs. be shipped for $234,78 ? Ans. 480 miles 3. An ufurer put out 75 dollars, at intereft; and at the end of 8 months received for principal and intereft, 79 | dollars; I demand at what rate per cent he received intereft ? Ans. 8 per cent. 4. If 7 men can make 84 rods of wall in 6 days; in what time will 10 men make 150 rods? . Ans. 7 days. 5. If the freight of 9hhd. of fugar, each weighing 12 Cwt. 20 leagues, coft 16: what must be paid for the freight of 50 tierces ditto, each weighing 21Cwt. 100 leagues? Ans. 92 11 10. § 9. Practice. "PRACTICE is a contraction of the Rule of Three Direct, when the first term happens to be an unit, or one; it has its name from its daily use among Merchants and Tradesmen, being an easy and concife method of working most questions, which occur in trade and business. PROOF. By the Single Rule of Three, Compound Multiplication, or by varying the parts. Before any advances are made in this rule, the Learner must commit to memory, the following |