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time, 6mo. 20d., or 6 mo., being, zo of 200 months, we take to of the principal, equal $88, as the interest for the 6mo. 20d.; and the 6d. being jobs of 200 months, we take por of the principal, equal $ 2.64, as the interest for the 6d. We add together the interest for the parts of the whole time, and obtain, as by the first operation, $ 420.64 as the whole interest.

RULE 1. Find the interest of $ 1 for the given time, by reckoning 6 cents for every YEAR, 1 cent for every TWO MONTHS, and 1 mill for every 6 DAYS; then multiply the given principal by the number denoting that interest, and the product will be the interest required. Or,

RULE 2. Take such fractional part or parts of the principal as the number expressing the time is of 200 months.

NOTE 1.- To find the amount, add the principal to the interest.

NOTE 2. — In computing interest for a fractional part of a month, the month is considered as consisting of 30 days. This has the sanction of general usage and the decisions of the courts, though not entirely accurate.

NOTE 3. Questions in interest, like other exercises in percentage, may be solved by proportion. The foregoing example admits of a statement and solution by the rule of compound proportion (Art. 340).

NOTE 4. It is customary among merchants to reject the mills in the results of their computations of interest, increasing, however, the number of cents by 1 when the decimal of a cent exceeds ó.

EXAMPLES.

years ?

years ?

2. What is the interest of $ 675 for 1 year? Ans. $ 40.50 3. What is the interest of $ 3967.87 for 2 years ?

Ans. $ 47 6.144 4. What is the interest of $ 896.28 for 3

Ans $ 161.33 5. What is the amount of $ 716.57 for 4 years ? 6. What is the amount of $ 76.47 for 7

Ans. $ 108.587 7. What is the interest of $ 123.45 for 6 years ?

Ans. $ 44.442 8. What is the interest of $ 750 for 12 years ?

Ans. $ 540 9. What is the interest of $ 130 for 2 months ? 10. What is the interest of $ 85 for 3 months ?

Ans. $ 1.275. 11. What is the interest of $ 19.62 for 7 months ?

Ans. $ 0.6867. 12. What is the interest of $ 637 for 10 months ?

13. What is the interest of $ 1671.32 for 14 months ?

Ans. $ 116.99. 14. What is the interest of $ 891.24 for 9 months ?

Ans. $ 40.10. 15. What is the interest of $ 91 for 5 days? Ans. $ 0.0758. 16. What is the interest of $ 324.66 for 18 days? 17. What is the interest of $ 3246 for 27 days?

Ans. $ 14.607. 18. What is the interest $ 1364.24 for 1 day? 19. What is the interest of $ 6444 for, 29 days ? 20. What is the amount of $18.60 for 24 days? 21. What is the interest of $ 386.19 for 100 months ?

Ans. $ 193.09. 22. What is the interest of $ 0.75 for 75 years ?

Ans. $ 3.371. 23. What is the interest of $ 396.15 for 1 year 1 month and 9 days?

Ans. $ 26.343. 24. What is the interest of $ 36.18 for 3 months and 7 days?

Ans. $ 0.584. 25. What is the interest of $ 97.15 for 2 years 11 months and 27 days?

26. What is the interest of $ 76.891 from January 11, 1852, \ to July 27, 1863 ?

Ans. $ 53.262. 27. What is the interest of $ 98.25 from July 4, 1856, to October 19, 1859 ?

Ans. $ 19.404. 28. What is the interest of $ 22.763 from February 19, 1836, to July 18, 1860 ?

29. What is the interest of $ 175.07 from January 7, 1855, A to October 12, 1859 ?

Ans. $ 50.04. 30. What is the interest of $197.281 from December 6, 1852, to January 11, 1854 ?

Ans. $ 12.987. 31. What is the amount of $ 4377.15 for 3 years ?

32. What is the interest of $ 444.60 for 5 years and 6 months ? y!

Ans. $ 146.718. 355. To find the interest of

money

rate per cent. for any given time.

Ex. 1. What is the interest of $ 84.50 at 7 per cent. for 2 years 5 months and 12 days?

Ans. $ 14.49.

any sum of

at any

FIRST OPERATION.

SECOND OPERATION.

Having found the Principal,

$8 4.50

interest for 1 year, Rate

per
cent.

.07

and then for 2 years,

the interest for 5 Interest for 1 year,

5.9 150

months is obtained 2

by first taking of Int. for 2 years,

11.8 3 0 0

1 year's interest,

for 4 months, and Int. for 4mo., or of lyr. 1.9 71 6

then of this last Int. for 1mo., or ļof 4mo. .49 29

interest for 1 month. Int. for 10d., or 1 of 1mo. .1 6 4 3

And since 10 days Int. for 2d., or } of 10d.

.03 28+

are 1 of 1 month, Int. for 2yr. 5mo. 12d. $ 1 4.4 9 16+ Ans. month's interest for

we take ţ of i

the interest of 10 days; and since 2 days are } of 10 days, we take of the last interest for 2 days. The interest as found for the several parts of the whole time, added together, gives the interest required.

We first find the inPrincipal,

$8 4.5 0

terest on the given sum Int. of $1 at 6 per cent. .1 47 at 6 per cent., and then

add to this interest the 5 9 150

fractional part of itself, 3 3800

denoted by the excess 8 450 of the rate above 6

per

cent. This excess is 1 Int. at 6 per cent. 1 2.4 2 1 5 0

per cent. ; therefore we # of int. at 6 per cent.

2.0 7 0 2 5

add of the interest at Int. at 7 per cent. $ 1 4.4 9 17 5 Ans. 6 per cent. to that in

terest for the answer. If the rate per cent. had been less than 6 per cent, we should have subtracted the fractional part.

Rule 1.— First find the interest for one year by multiplying the principal by the rate per cent. expressed decimally;" and for two or more years multiply this product by the number of years.

Find the interest for months by taking the most convenient fractional part or parts of ONE year's interest.

Find the interest for days by taking the most convenient fractional part or parts of ONE month's interest. Or,

RULE 2.— Find the interest of the given sum at 6 per cent., and then add to this interest, or subtract from it, such a fractional part of itself as the given rate is greater or less than 6 per

NOTE 1. — of the interest at 6 per cent. may be taken for that at 1 per cent.; Į, for that at 1} per cent. ; }, for that at 2 per cent.; s, for that at 3 per cent. From the interest at 6 per cent. may be taken of itself for that at 4 per cent.; of itself for that at 45 per cent.; and 1 of itself for that at 5 per cent. To the interest at 6 per cent. may be added ¿ of itself for that at 7 per

cent.

cent.; of itself for that at 7} per cent.; } of itself for that at 8 per cent ; and

of itself for that at 9 per cent. If the rate is 12 per cent., the interest at 6 per cent. may be taken twice; if 18 per cent., the interest at 6 per cent. may be taken three times, etc.

NOTE 2. - When in this book the rate of interest is not given, 6 per cent. is to be understood.

EXAMPLES.

X2. What is the interest of $ 16.75 for 7 months and 17 days, at 7 per cent. ?

Ans. $ 0.739. 3. What is the interest of $11.104 from April 17, 1852, to December 7, 1852, at 7 per cent. ?

Ans. $ 0.496. 4. What is the interest of $ 12.69, from January 2, 1853, to August 30, 1854, at 7 per cent. ?

Ans. $ 1.474. * 5. What is the interest of $ 5000 for 2 years 5 months 26 days, at 7 per cent. ?

6. What is the amount of $ 416 for 3 years 16 days, at 7 per cent. ?

Ans. $ 504.64. X7. What is the interest of $ 336 for 15 days, at 5 per cent. ?

Ans. $ 0.70. X 8. What is the interest of $ 17869.75 from February 7, 1852, to January 11, 1860, at 5 per cent. ?

Ans. $ 7083.3703. * 9. What is the interest of $300.50 for 1 year 2 months and 15 days?

Ans. $ 21.786. >10. What is the interest of $ 37 for 29 days, at 5 per cent. ? x11. What is the interest of $ 35.61 from November 11, 1861, to December 15, 1863?

Ans. $ 4.474. X12. What is the interest of $ 16.76 from December 17, 1841, to January 17, 1852?

Ans. $ 10.139+ X13. What is the interest of $ 1728.19 from May 7, 1854, to July 17, 1860, at I per cent. ?

Ans. $ 26.762. 14. What is the interest of $ 397.16 for 1 year 6 months and 1 day, at 51 per cent. ?

Ans. $ 32.826. *15. What is the amount of $ 100.25 for 2 months and 29 days, at 4 per cent. ?

Ans. $ 101.241. K16. What is the interest of $ 51.17 for 9 months and 29 days, at 4 per cent.?

Ans. $ 1.699. X17. What is the interest of $ 42.20 for 1 year and 16 days, at 41 per cent. ?

*18. What is the interest of $ 16.25 for 2 years, at 3 pet cent. ?

Ans. $ 0.975. * 19. What is the interest of $ 96.84 from November 27, 1849, to July 3, 1852, at 74 per cent. ? Ans. $ 18.883.

*20. What is the interest of $ 786.97 from October 19, 1857, to August 17, 1861, at 74 per cent.?

21. What is the interest of $ 71.091 from July 29, 1853, to June 19, 1857, at 12 per cent. ?

Ans. $ 33.175. x 22. What is the amount of $ 369.29 for 2 years

3 months and 1 day, at 9 per cent. ?

Ans. $ 444.163. + 23. What is the interest of $ 76.35 for 1 year 8 months and 18 days?

Ans. $ 7.864. 24. What is the interest of $ 47.15 for 1 month and 19 days, at 131 per cent. ?

Ans. $nama 866 25. What is the interest of $ 36.72 from May 16, 1829, to February 18, 1857, at 7 per cent.?

Ans. $ 71.342. x 26. What is the interest of $35.50 for 3 years 5 months and 20 days, at 7 per cent. ?

Ans. $ 8.628. 27. What is the amount of $ 496.30 for 6 months and 20 days, at 7 per cent. ?

Ans. $ 515.60. * 28. What is the interest of $ 691.04 for 1 month 3 days, at 5 per cent. ?

Ans. $ 3.167. 29. What is the interest of $ 9750 for 4 months, at 2 per cent. a month?

Ans. $ 780. 30. What is the interest of $ 9162 for 3 months, at 1per cent. a month ?

Ans. $ 412.29. 31. What is the interest of $ 1500 for 7 months 20 days, at 10 per cent. ?

Ans. $ 95.833. 32. What is the interest of $ 640.50 for 10 months and 26 days, at 10 per cent. ?

Ans. $ 58.00. 33. What is the interest of $ 3178 for 15 months and 15 days?

34. If a banker borrow $ 10,000 in Boston at 6 per cent., and let the same in Wisconsin at 7 per cent., how much does he make by the operation in that way in 2 years and 63 months ?

Ans. $ 255.555. 356. To reckon interest for any number of days, when 12 months of only 30 days each, or 360 days, are considered a year.

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