INTEREST. 240. Interest is compensation for the use of money. 241. The money for which interest is paid is called the principal. 242. The principal and interest together are called the amount. NOTE. Interest is usually reckoned in per cent, the principal being the base; that is, the borrower pays for the use of money a sum equal to a certain per cent of the principal. When a man loans money "at 6%" he expects to receive back the principal, and a sum equal to 6% of the principal for every year the money is loaned and at that rate for fractions of years. EXAMPLE. Find the interest of $257 for two years at 6%. Operation. $2'57 .12 5.14 25.7 $30.84 Explanation. The interest of any sum for 2 years at 6% is 12 hundredths of the principal. One hundredth of $257 is $2.57, and 12 hundredths of $257 is 12 times $2.57 or $30.84. 1. Find the interest of $242 for 3 yr. at 7%. 2. Find the interest of $375 for 2 yr. at 6%. 3. Find the interest of $146 for 1 yr. at 5%. 4. Find the interest of $274 for 3 yr. at 5%. 5. Find the interest of $375 for 2 yr. at 8%. 6. Find the interest of $864 for 3 yr. at 7%. (a) Find the sum of the six results. Interest. 243. TO COMPUTE INTEREST FOR ANY NUMBER OF YEARS NOTE. AND MONTHS. The interest for 1 month is 1 twelfth as much as it is for 1 year; for 2 months, 2 twelfths or 1 sixth, etc. EXAMPLE. Find the interest of $324.50 for 2 yr. 5 mo. at 6%. Operation and Explanation No. 1. Interest of $324.50 for 1 year at 1% = $3.245 Interest of $324.50 for 1 year Interest of $324.50 for 2 yr. 5 Operation No. 2. at 6% = $1.6225 at 6% at 6% = $19.470 = $38.940 8.1125 $47.0525 at 6% = Explanation. .141 $1.6225 1. Find the interest of $325.40 for 1 yr. 6 mo. at 7%. 2. Find the interest of $420.38 for 2 yr. 10 mo. at 6% 3. Find the interest of $221.60 for 2 yr. 3 mo. at 6%. 4. Find the interest of $145.20 for 1 yr. 9 mo. at 5%. 5. Find the interest of $340.10 for 3 yr. 1 mo. at 4%. (a) Find the sum of the five results. Interest. 244. TO COMPUTE INTEREST FOR ANY NUMBER OF YEARS, MONTHS, AND DAYS. NOTE. In computing interest, 30 days is usually regarded as 1 month, and 360 days as 1 year; so each day is of a month or so of a year. EXAMPLE. Find the interest of $256.20 for 2 yr. 7 mo. 13 days at 6%. Operation and Explanation No. 1. Interest of $256.20 for 1 yr. Operation No. 2. 2 yr. 7 mo. 13 da. 2333 yr. 2223 times .06 .15 -360 = $2'56.20 1.8361 12.8100 25.620 $40.2661 at 6% = at 1%= == $2.5620 at 6% = $15.3720 $30.7440 at 6% = $1.2810 at 6% = $8.9670 $.04270 .5551 43 of 1 hundredth of $256.20 is $1.8361 5 hundredths of $256.20 is $12.81 10 hundredths of $256.20 is $25.62 1543 hundredths of $256.20 is $40.2661 PROBLEMS. 1. Find the interest of $350.40 for 2 yr. 5 mo. 7 da. at 6%. 2. Find the interest of $145.30 for 1 yr. 7 mo. 10 da. at 8%. 3. Find the interest of $174.20 for 2 yr. 3 mo. 15 da. at 7%. (a) Find the sum of the three results. 245. The "six-per-cent_method.” NOTE.-If the teacher so prefers, the problems on the three preceding pages, as well as those that follow, may be solved by the "sixper-cent method." EXPLANATORY. The interest at 6% for 1 yr. = .06 of the principal. of .06, or .005 of the principal. of .005, or .0001 of the principal. The interest at 6% for 1 day = 30 READING EXERCISE. 1. Interest for 1 yr. at 6% =-100ths of the principal; = -1000ths; Find the interest of $243.25 for 2 yr. 5 mo. 18 da. at 6%. Operation and Explanation. Interest for 2 yr. .12 of the principal. = Interest for 5 mo. .025 of the principal. Total interest = .148 of the principal. (1) $36.001 plus of $36.001 time at 7%. = int. of same prin. for the same (2) $36.001 less of $36.001 int. of same prin. for the same time at 5%. (3) How find the interest at 8%? At 9%? At 4%? At 3%? Interest. 246. PROBLEMS TO BE SOLVED BY THE SIX PER CENT 1. Find the interest of $265 for 1 yr. 3 mo. 13 da. at 6%.* 2. Find the interest of $346 for 2 yr. 5 mo. 20 da. at 6%.† 3. Find the interest of $537 for 1 yr. 7 mo. 10 da. at 6%.‡ 4. Find the interest of $428 for 3 yr. 3 mo. 14 da. at 6%. 5. Find the interest of $150 for 1 yr. 6 mo. 15 da. at 6%. (a) Find the sum of the five results. 6. Find the interest of $245.30 for 6 mo. 18 da. at 7%. 7. Find the interest of $136.25 for 8 mo. 10 da. at 7%. 8. Find the interest of $321.42 for 5 mo. 15 da. at 7%. 9. Find the interest of $108.00 for 10 mo. 8 da. at 7%. 10. Find the interest of $210.80 for 7 mo. 21 da. at 7%. (b) Find the sum of the five results. 11. Find the amount of $56.25 for 2 yr. 4 mo. 2 da. at 6%. 12. Find the amount of $31.48 for 1 yr. 5 mo. 11 da. at 6.%. 13. Find the amount of $55.36 for 2 yr. 8 mo. 12 da. at 6%. 14. Find the amount of $82.75 for 2 yr. 10 mo. 8 da. at 6%. 15. Find the amount of $27.35 for 1 yr. 1 mo. 1 da. at 6%. (c) Find the sum of the five results. 16. Find the amount of $875 for 3 yr. 8 mo. 15 da. at 5%. 17. Find the amount of $346 for 2 yr. 6 mo. 12 da. at 4%. 18. Find the amount of $500 for 1 yr. 7 mo. 18 da. at 3%. 19. Find the amount of $600 for 2 yr. 5 mo. 21 da. at 8%. 20. Find the amount of $825 for 1 yr. 9 mo. 24 da. at 9%. (d) Find the sum of the five results. |