3. What debt will be discharged in a year, or twelve months, by paying il. the first month, 21. the second, 4). the third, and so on, each succeeding payment being double the last ; and what will the last payment be? Ans. The debt is 40951. and the last payment 20481. SIMPLE INTEREST, INTEREST is the premium, allowed for the loan of money. The sum lent is called the principal. The sum of the principal and interest is called the amount. Interest is allowed at so much per cent. per annum, which premium per cent. per annum, or interest of 100l. for a year, 'is called the rate of interest, Interest is of two sorts, simple and compound. Simple interest is that, which is allowed only for the principal lent. NOTE. Commission, Brokerage, Insurance, Stocks, * and, in general, whatever is at a certain rate, or sum per' cent. are calculated like Simple Interest. 1. Multiply the principal by the rate, and divide the product by 100; and the quotient is the answer for one year. 2. Multiply * Stock is a general name for public funds, and capitals of trad. ing companies, the shares of which are transferable from one person to another. + The rule is evidently an application of Simple Proportion and Practice. 2. Multiply the interest for one year by the given time, and the product is the answer for that time. 3. If there be parts of a year, as months or days, work for the months by the aliquot parts of a year, and for the days by Simple Proportion. RXAMPLES. 1. What is the interest of 450l. for a year, at 5 per cent. per annum ? 2. What is the interest of 720l. for 3 years, at 5 per cent. per annum ? 3. What is the interest of 1701. for 1 year, at 5 per cent. per annum ? 1701. 2)81. 10s, interest for 1 year. 5 4 5 121. 155. Answer. 8.50 20 10:00 4. What 4. What is the interest of 1071. for 117 days, at 4 per cent. per annum? 1071. 5 17 32 $7 3'2 7 35 11 6 24 428 55 18 1 3:2 IO 26 15.7 11 X 10+7=117 559 I бо 5'08 5 35 II 6 2.4 20 365)594 13 O 2:4(1l. 128. 778e5d. 1.65 365 the answer. 12 229 20 4 )4593 3:20 305 7.80 9. .. 2'4=2=d. 943 730 213 92556 1} 5. What is the interest of 321. 5s. 8d. for 7 years, at 45 per cent. per annum ? Ans. 91. 125. 178od. 6. What is the interest of 3191. 6d. for 5 years, at 3 per cent. per annum ? Ans. 681. 155. od. 27.9. 7. What is the interest of 607*50D. for 5 years, at 6 per cent. per annum ? Ans. 182.25D. 8. What is the interest of 2131. from Feb. 12, to June 5, 1796, it being leap year, at 31 per cent. per annum? Ans. 21. 6s. 6d. 378259. SIMPLE INTEREST BY DECIMALS. . RULE.* Multiply continually the principal, ratio and time, and it will give the interest required. Ratio is the simple interest of 1l. for 1 year, at the rate per cent. agreed on ; thus the ratio * The following theorems will shew all the possible cases of simple interest, where p = principal, i = time, r = ratio, and EXAMPLES. 1. What is the interest of 945l. 1os. for 3 years, at 5 per cent. per annum ? 2. What is the interest of 7961. 155. for 5 years, at 4 per cent. per annum ? Ans. 1791. 58. 4 . 3. What is the interest of 5371. 155. from November 11, 1764, to June 5, 1765, at 3 per cent. ? Ans. iil. d. COMMISSION. COMMISSION is an allowance of so much per cent. tó a factor or correspondent abroad, for buying and selling goods for his employer. EXAMPLES |