SIMPLE INTEREST REVIEWED ORAL EXERCISE Find the interest on the following sums for the times and at the rates specified: 1. $2 for 1 yr. at 5%; at 6%. 2. $25 for 1 yr. at 4%; at 2%. 3. $300, at 5%, for 1 yr.; for 2 yr. 4. $400, at 5%, for 1 yr.; for 3 yr. 5. $500, at 6%, for 1 yr.; for 6 mo. 6. $700, at 6%, for 1 yr.; for 1 yr. 7. $400, at 6%, for 2 yr.; for 2 yr. 6 mo. 8. $250, at 4%, for 1 yr.; for 1 yr. 6 mo. 9. $1000, at 5%, for 3 yr.; for 3 yr. 6 mo. 10. $2500, at 4%, for 1 yr.; for 2 yr.; for 24 yr. 11. $3000, at 6%, for 1 yr. 6 mo.; for 1 4 mo. yr. 12. $2000, at 5%, for 1 yr. 6 mo.; for 2 yr. 6 mo. 13. $1500, at 3%, for 1 yr.; for 2 yr.; for 1 yr. 4 mo. 14. $5000, at 6%, for 1 yr.; for 3 yr.; for 6 mo.; for 3 mo.; for 1 mo.; for 15 da. Find the amount of principal and interest together, given the following principals, rates, and times: 15. $100, at 6%, for 1 yr.; for 2 yr. 16. $300, at 5%, for 1 yr.; for 2 yr. 17. $250, at 4%, for 1 yr.; for 3 yr. 18. $500, at 4%, for 1 yr.; for 5 yr. 19. $1000, at 41%, for 1 yr.; for 2 yr. 20. $2000, at 5%, for 1 yr.; for 2 yr. 404. Illustrative problem. Find the interest on $500, at 6%, for 2 yr. 3 mo. 6 da. 1. The interest for 1 yr. is 6% of $500, or $30. $68.00 3. Therefore the total interest is 405. How to find interest. Therefore, to find interest, Find the interest for one year, and multiply by the number of years or the part of a year. WRITTEN EXERCISE 1. Find the interest on $275 for 3 yr. 6 mo. at 5%. 2. Find the interest on $1250 for 7 yr. 11 mo. at 6%. 3. Find the interest on $630 for 2 yr. 4 mo. 5 da. at 6%. 4. Find the interest on $345 for 2 yr. 3 mo. 3 da. at 5%. 5. Find the interest on $290 for 1 yr. 6 mo. 5 da. at 5%. 6. Find the interest on $350 for 1 yr. 9 mo. 15 da. at 4%. 7. Find the interest on $650 for 2 yr. 8 mo. 10 da. at 6%. 8. Find the interest on $1575 for 3 yr. 1 mo. 6 da. at 51%; at 41%; at 6%. 9. A man borrowed $250 on January 15, at 6%. He paid the principal and interest on October 15. How much did he pay? 10. A man borrowed $350 on January 27, at 6%. He paid the principal and interest on February 27 of the following year. How much did he pay? 11. A man bought 12 head of cattle on February 1, at $45 a head, giving his promissory note at 6%. He paid it on the 16th of the following April. What was the amount of principal and interest? 406. Cancellation used in interest. It is often advisable to shorten the work by cancellation. Find the interest on $256.75 for 2 yr. 2 mo. 10 da. at 41%. Since 41%%=286, and 2 yr. 2 mo. 10 da.=(730+60+10) da. = 800 da., we have When the time exceeds 1 yr., and cancellation is used, it is better to take 365 da. to the year. Of course this gives exact interest, as described on page 370. WRITTEN EXERCISE Find the interest, given the principal, time, and rate: 1. $172.60, 3 yr. 2 mo. 7 da., 4%. 2. $391.75, 3 yr. 8 mo. 17 da., 4%. 3. $235.50, 3 yr. 1 mo. 9 da., 6%. 4. $175.50, 2 yr. 8 mo. 10 da., 6%. 5. $142.80, 1 yr. 3 mo. 15 da., 5%. 6. $273.40, 2 yr. 8 mo. 20 da., 5%. 7. $172.60, 2 yr. 5 mo. 6 da., 41%. 8. $182.60, 4 yr. 8 mo. 17 da., 51%. 9. $163.40, 3 yr. 9 mo. 15 da., 5%. 10. $625.50, 2 yr. 11 mo. 25 da., 53% 11. $475.50, 3 yr. 10 mo. 15 da., 41%. 12. $265.50, 2 yr. 10 mo. 20 da., 43%. 13. $3562.50, 3 yr. 2 mo. 5 da., 51%. 407. The Six Per Cent Method. The following short method, known as the Six Per Cent Method, is often convenient. Required the interest on $420 for 5 mo. 10 da. at 6% 1. Since 2 mo. = yr., the rate for 2 mo. = of 6% = 1%. 2. Therefore the int. for 2 mo. = 1% of $420 and for 66 66 = $4.20 2 mo. more, 4.20 66 1 mo. 66 of $4.20, 10 da. 66 of $2.10, 3. Therefore the total interest is 2.10 .70 $11.20 Therefore the interest at 6% for 60 days is 0.01 of the principal, for 6 days 0.001 of the principal, and for other periods the interest can be found from the interest for these periods. Various other forms of this method are given, but none is so simple as the above. This is sometimes spoken of as the Banker's Method. The following method may be taken, if desired, in which case the above should not be taken. Since the rate for 1 yr. is 18 of the principal, 408. Multiply the principal by 6 times the number of years and the number of months as hundredths, adding the prod uct of the principal by the number of days as thousandths. Thus, to find the interest, at 6%, on $120, for 2 yr. 3 mo. 9 da.: |