NOTE. With very little practice the pupil will, without making a figure, mentally determine the interest of $1 for any length of time. This habit is very desirable, as it will greatly facilitate the computation of interest. 3. What is the interest of $1 for 3yr. 1m. 15d.? Ans. $.187. 4. What is the interest of $1 for 1yr. 3m. 29d.? 5. What is the interest of $1 for 4yr. 2m. 4d.? Ans $.0798. Ans. $.2503. 6. What is the interest of $1 for 4yr. 3m. 17d.? 7. What is the interest of $1 for 4yr. 9m. 12d.? 8. What is the interest of $1 for 10yr. 11m. 7d.? 9. What is the interest of $1 for 2yr. 11m. 5d.? 10. What is the interest of $1 for 1yr. 8m. 3d.? 233. To find the interest of any sum at 6 per cent. for any given time. The interest of $2 is evidently twice as much as the interest of $1; so the interest of $3, $4, or $7, is 3, 4, or 7 times the interest of $1; and the interest of $2.25 is 2.25 (i. e. 2 and 25 hundredths) times the interest of $1; .. to find the interest of any number of dollars we have only to find the interest of $1, and then multiply the interest by the number of dollars in the principal. 11. What is the interest of $2 for 1yr. 5m. 9d.? $.086 interest of $1 for lyr. 5m. 9d. 2 $.173 interest of $2 for lyr. 5m. 9d., Ans. 12. What is the interest of $6.50 for 3yr. 8m. 18d.? $.223 interest of $1 for 3yr. 8m. 18d. = 6.5 0 11150 1338 $ 1.4 4 9 5 0 = interest of $6.50 for 3yr. 8m. 18d., Ans. 232. What is the Note? 233. Rule for finding the interest of any sum at 6 per cent., for any time? Reason? 13. What is the interest of $300 for 2yr. 7m. 24d.? $.159 = interest of $1 for 2yr. 7m. 24d. 300 $ 47.7 0 0 = interest of $300 for 2yr. 7m. 24d., Ans. 14. What is the interest of $700 for 1yr. 9m. 12d.? Ans. $74.90. 15. What is the interest of $400 for 2yr. 6m. 15d.? 16. What is the interest of $350 for 3yr. 8m. 24d.? 234. The mode of casting interest given in Art. 233 is per fectly simple, but the product is not changed when the multiplicand and multiplier change places (Art. 59, Note). Hence, To cast interest at 6 per cent. per annum, on any sum, for any time, RULE. Multiply the principal by the decimal which represents the interest of $1 for the given time. 17. What is the interest of $468 for 2yr. 6m. 11d.? 234. Second rule? Why correct? In like manner, when the multiplier is, we may divide by 3 and set down the quotient twice. Reason? Easiest way of multiplying by five sixths? Easiest way for two thirds? 18. What is the interest of $48.50 for 2yr. 7m. 21d. ? Ans. $7.68725. 19. What is the interest of $248 for 2yr. 3m. 18d.? Ans. $34.224. 20. What is the interest of $965.188 for 2yr. 3m. 11d.? Ans. $132.07—. NOTE 1. In the 20th example the Ans. is $132.069891, but this, in all ordinary business transactions, would be called $132.07. In the following examples in interest only 3 decimal places in the product will be preserved, but if the 4th decimal place is 5 or more, the third place will be increased by 1 thousandth. 21. What is the interest of $225.87 for 1yr. 3m. 15d.? Ans. $17.505. 22. What is the interest of $35.40 for 2yr. 6m. 9d.? Ans. $5.363. 23. What is the interest of $450.87 for 1yr. 7m. 9d.? 24. What is the interest of $375.50 for 2yr. 1m. 8d.? 25. What is the interest of $225.75 for 1yr. 5m. 12d.? 26. What is the interest of $84.82 for 2yr. 4m. 18d.? 27. What is the interest of $125.16 for lyr. 11m. 25d.? 28. What is the interest of $658.25 for 1yr. 2m. 13d.? 29. What is the interest of $125 from June 7, 1851, to Feb. 11, 1854? Ans. $20.083. NOTE 2. Ex. 29 differs from the preceding only in its being necessary to find the time (Art. 203). 30. Find the interest of $154.25 from April 18, 1852, to Jan. 26, 1855. Ans. $25.657. 31. Find the interest of $172 from Aug. 7, 1854, to Sept. 9, 1856. 32. Find the interest of $254 from Nov. 12, 1855, to Jan. 30, 1857. 33. What is the interest of $132.25 from Nov. 13, 1836, to May 2, 1841? 34. What is the interest of $100 from March 26, 1841, to June 21, 1842? 234. What of decimal places after the third in the Ans.? Explain Ex. 29. 235. To find the interest when the principal is in pounds, shillings, pence, and farthings: RULE. Reduce the lower denominations to the decimal of a pound (Art. 175), then proceed as with dollars and cents, and finally reduce the decimal part of the interest back to shillings, pence, and farthings (Art. 176). NOTE. But 3 decimal places in the multiplicand are used. yr. 35. What is the interest of 56£ 10s. 6d. 3qr. for 1 24d. ? Ans. 5£ 6s. 3d. 1qr. 6m. 36. What is the interest of 246£ 18s. 9d. 1qr. for 2yr. 3m. 15d.? 37. What is the interest of 125£ 16s. 8d. 2qr. from Nov. 13, 1861, to March 26, 1863? 236. To find the interest of any sum for any time, at any other rate than 6 per cent.: RULE. First find the interest at 6 per cent.; then divide this interest by 6, which will give the interest at 1 per cent.; and, finally, multiply the interest at 1 per cent. by the given rate. 38. What is the interest of $124.50 for 1yr. 4m. 12d., at 5 per cent.? OPERATION. $ 12 4.5 0, Principal. .082= Int. of $1 at 6 per cent. for 1yr. 4m. 12d. 24900 99600 6) $10.20900 Int. of Principal at 6 per cent. $ 1.7 0 1 5 Int. of Principal at 1 per cent. Int. of Principal at 5 per cent., Ans. 5 $8.50 75 39. What is the interest of $342.25 for lyr. 9m. 18d., at 8 per cent.? Ans. $49.284. 235. Rule for casting interest on pounds, shillings, etc.? How many decimal places in the multiplicand are used? 236. Rule for computing interest at any given rate? 40. What is the interest of $256.84 for lyr. 3m. 15d., at 9 per cent.? 41. What is the interest of 24£ 6s. 8d. 1qr. for 2yr. 9m. 12d., at 5 per cent.? Ans. 3£ 7s. 8d. 3qr. 42. What is the interest of 150£ 10s. for 2yr. 4m. 6d., at 4 per cent.? 237. any time: To find the amount of any sum at any rate for RULE. First find the interest by the preceding rules, and to the interest add the principal. 43. What is the amount of $325.75 for lyr. 4m. 24d., at 6 per cent.? 44. What is the amount of $224.48 for 2yr. 6m. 15d.? Ans. $258.713. 45. What is the amount of $48.33 for 1yr. 6m.? 46. What is the amount of $365.25 for lyr. 3m. 9d.? 47. What is the amount of $444 from July 18, 1861, to Sept. 4, 1862? 48. What is the July 25, 1862, at 7 49. What is the Ans. 474.044. amount of $32.25 from Nov. 15, 1860, to per cent.? amount of $187.44 from May 25, 1859, to April 19, 1861, at 7 per cent.? 50. What is the amount of 82£ 12s. 6d. 3qr. from Feb. 12. 1860, to Dec. 24, 1862, at 5 per cent.? 237. Rule for finding the amount of any sum for a given time and rate? 238. Rule for casting interest on notes when partial payments have been made? Exception? Explain Ex. 51. |