and that the interest added] This sum of 7 dollars is the to the principal makes a sum rate per cent. per annum, or, called the amount, viz. 76.59 by the hundred by the year. dollars. Subtract the principal 74, from 76.59 the amount, the LESSON 12. What is the interest of 130 difference 2.59 is the interest. dollars for 73 days at 6 per Then say: If 74 dollars cent. per annum? principal in 6 months, will Answer, 156 cents. give 2.59 dollars interest,dol. P. days. dol intr. 100 130 : 73 : 130 x 73 x 6 = 56940 for Second term, 365 Divisor, 36500 36500)56940(156 cents. 36500 204400* : 100 259.00 12 .219000* 219000 * Decimals annexed. CONTRACTED PROPORTION, OR, CONTRACTIONS IN THE RULE OF THREE. RULE 1. Divide the second term by the first, and multiply that quotient by the third. EXAMPLE. If 3 yards of cloth cost £3 18s. 6d. what will 12 yards Answer, £15 148. cost? Divide the first term by the third, and divide the second by that quotient. EXAMPLE. Bought 4 parcels of indigo, each 3 pounds, for 39 dol, or, 3900 cents; how much did 5 pounds cost? Divide the third term by the first, and multiply that quo tient by the second. EXAMPLE, Bought 5 bushels of salt for £2 2s. 1d. what will 25 bushels cost at that rate? bu. £. s. d. bush. 5 5:2 2 1 :: 25 5)25 Quotient & multiplier, RULE 4. Divide the first term by the second, and divide the third by that quotient. EXAMPLE. If I give 7 dol. and 50 cents for 30 lb. sugar, what must be paid for a hundred or 56 lb.? Ans. 14 dollars. A decimal added to balance the decimal in the divisor. Divide the first term by the third, and multiply the second by that quotient. EXAMPLE. If I have 36 cwt. carried 50 miles for 18 dollars, how I have 12 cwt. carried for the same money far may ? Answer, 150 miles. Suppose a school to consist of 32 pupils, subscribed for by the proprietors; that a Master teaches during the term of one quarter, or 71.5 days, at 17 dollars and 16 cents a month, and his wages amount to 51 dollars 48 cents; that the whole number of days which each scholar has attended, being added together, make 2288; and that A, has sent 214.5 days, B, 71.5, C, 143, &c. how shall we know what each man has to pay, without making a statement in the Rule of Three for each one's quota? RULE. 1. As the whole number of days, is to the whole sum; So is one day, to a common multiplier. 2. Multiply each man's number of days by this common multiplier, the product will be the quota sought. When the first decimal figure happens over five, add one cent. For instance, make A's quota 83, B's 61, and C's 22, rejecting the fractions. INTEREST. Interest is a sum of money allowed by the borrower to the lender. For instance, A, borrows 400 dollars of B, for one year, and agrees to pay B, 7 dollars for the use of every hundred dollars. This is called 7 per cent.; 7 dollars being the rate per cent.* In this case the sum 400 dollars is called the principal, 28 dollars the interest, and the interest added to the principal, makes 428 dollars, which sum is called the amount. LESSON 1. If 100 dollars in 1 year will give 7 dollars interest, what will 400 dollars give in five years. Ans. 140 dolls. Rate per cent., signifies, a price fixed by the hundred. Rate per cent!, per annum, signifies, a price fixed by the hundred by the year. Although interest is calculated by the Rule of Three, yet there is a short and easy way without a formal state ment. RULE Multiply the principal by the rate per cent. and divide that product by 100, the quotient will be the interest for one year. Then, multiply the interest of one year by the time, the product will be the answer. EXAMPLE. Interest, 28100 This number 2800 is divided by 100. Years. 140 dollars interest in 5 years. LESSON 2. What is the amount of a note of hand for 14 dollars 37 cents on interest 2 years, at 7 per cent. per annum ? Answer, $16 38.75 cents. Reduce the given sum or principal to cents. 14 dolls. 374 cents 1437.5 cents. 7 per cent. 10062.5 1437.5 cents. Here the interest for two years appears to be 201 cents and .25 hundredths of a cent; which sum added to the principal, makes 1638.75 cents, or, 16 dollars 38 cents and 201125.0 divided by 100.75 hundredths of a cent. 1437.5 cents, principal. 2 years. Statement, 201.25 1638.75 amount. interest. LESSON 3. See Card 32. What is the interest of £ 13 17s. 6d. for 1 year at 6 per cent. ? Ans. £Q 16s, 7d. 3qrs. and 20 hundredths of a farthing. |