Q. What is Interest? What is the money called on which interest is paid? What is the money called which is paid for the use of the principal? What is the amount? What determines the rate of interest? What is the meaning of per cent? What is legal interest? What is meant by per annum? How much is the interest per annum in most of the states? What is it in New York? CASE I. § 153. To find the interest on any given principal for one or more years. EXAMPLES. per cent? OPERATION. 100 6 650: Ans. 6 1. What is the interest of $650 for one year at 6 It is plain, that $100 is to $6, its interest for one year, as $650 to its interest for the same time. The fourth term is found by multiplying the second and third terms together and dividing by the first $140. 100)3900 Ans. $39,00. 2. What is the interest on $950 for four years at 7 per cent per annum? I. Multiply the principal by the rate of interest, and divide the product by 100: the quotient will be the interest for one year. II. When the number of years exceeds one, multiply the interest for one year by the number of years: the product will be the interest for that number of years. 3. What is the interest on $3675 for three years, at 7 per cent per annum? Ans. $771,75. 4. What is the interest on $459 for five years at 8 per cent per annum? Ans. $183,60. 5. What is the interest of $327,45 for one year at 6 per cent per annum? We first multiply the given sum $327,45 by the rate of interest, 6 per cent, leaving two places for decimals or cents at the right hand. Then to divide by 100 we remove the decimal point two places to the left, leaving four places for decimals to the right hand. OPERATION. $327,45 6 100)1964,70 Ans. 19dolls. 64cts. 7m. If the principal had contained mills, there would have been five places of decimals in the answer. Hence, we have the following RULE. I. When the principal contains dollars only, multiply by the rate of interest, and point off two places from the right hand for cents: the places on the left will express the dollars. II. When the principal contains dollars and cents, multiply as before, and strike off four places from the right hand for cents and mills. III. When the principal contains dollars, cents and mills, multiply as before and strike off in the product five places from the right hand: the places to the left will be dollars. Q. When the principal is in dollars, how do you find the interest for one year? How do you find the interest for two or more years? When the principal contains dollars and cents, how do you find the interest? When the principal contains dollars, cents and mills, how do you find the interest? 6. What is the interest on $375, 27cts. 3m. for two at 7 per cent per annum? years, 7. What is the interest on $211,26 for one year at 41 per cent per annum? 8. What is the interest on $1576,91 for 3 years at 7 per cent? Ans. $331,15+. 9. What is the interest on $957,08 for 6 years at 31 per cent? Ans. $200,98+. 10. What is the interest on $375,45 for 7 years at 7 per cent per annum? Ans. $183,970+. 11. What is the interest on $4049,87 for 2 years at 5 per cent per annum? Ans. $404,98+. CASE II. § 154. To find the interest at 6 per cent per annum for any number of months. At six per cent per annum, each month produces per cent on the principal; and every two months produces one per cent on the principal. Therefore, to find the interest for months we have the following RULE. Multiply the principal by half the number of months, and remove the separating point in the product two places farther to the left hand. EXAMPLES. 1. What is the interest of $327 for 8 months at 6 per 2. What is the interest of $327,47 for 9 months at 3. What is the interest on $8975 for ten months at 6 per cent per annum? Ans. $448,75. 4. What is the interest on $8753,65 for fourteen months Ans. $612,7555. at 6 per cent per annum ? 5. What is the interest on $37596,42 for sixteen months at 6 per cent per annum? Ans. $3007,7136. 6. What is the interest on $3976,85 for nine months at 6 per cent per annum? Ans. $178,9582. Q. How do you find the interest at 6 per cent for any number of months? What per cent will two months give? Five months? Six months? Seven months? Nine months? Eleven months? Twelve months? CASE III. Four months? Eight months? § 155. To find the interest at 6 per cent per annum, for any number of days. In computing interest the month is reckoned at 30 days. Hence, 60 days, which make two months, will give an interest of one per cent on the principal. This one per cent is found by simply removing the separating point two places to the left. If this one per cent be then divided by 60 the quotient will be the interest for 1 day, and this quotient multiplied by the number of days will give the interest required. To divide by 60 we remove the separating point one place farther to the left, and then divide by 6. Hence, we have the following RULE. I. Remove the separating point in the principal three places to the left, then divide by 6 and the quotient will be the interest for 1 day. II. Multiply the interest by the number of days, and the product will be the answer sought. EXAMPLES. 1. What is the interest on $327,30 for 25 days? 2. What is the interest on $27,25 for 19 days? 3. What is the interest on $575,72 for 29 days? Ans. $2,78+. 4. What is the interest on $195,19 for 7 days? Ans. $0,22+. 5. What is the interest on $897,04 for 27 days? Ans. $4,0366+. 6. What is the interest on $378,53 for 18 days? Ans. $1,135+. 7. What is the interest on $885,62 for 25 days? Ans. $3,69+. 8. What is the interest on $3756,25 for 17 days? NOTE. The above method of computing interest is the one in general use, though it gives the interest a trifle too large, as it considers the year at 360 instead of 365 days. If entire accuracy is required, find the interest for one year-then multiply by the number of days, and divide the product by 365. |