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

Ans. $ 0.975.

19. What is the interest of $96.84 from November 27, 1849, to July 3, 1852, at 71⁄2 per cent.? Ans. $18.883.

20. What is the interest of $786.97 from October 19, 1857,

to August 17, 1861, at 7 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. 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 13 per cent.? Ans. $ 0.886. 25. What is the interest of $36.72 from May 16, 1829, to February 18, 1857, at 7 per cent.? Ans. $71.342. 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.?

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Ans. $515.60.

28. What is the interest of $ 691.04 for 1 month 3 days, at 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 14 per 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.

Ex. 1.

What is the interest of $ 460 for 93 days?

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We multiply the principal by of the number of days, considered as thousandths; since the interest of $1 at 6 per cent. for 6 days is 1 mill or 1 thousandth of a dollar, (Art. 352,) and for any other number of days, at the same per cent., must be

one sixth as many mills or thousandths of a dollar as there are

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Ans. $7.1 3 30 days+3 days.

Interest for 93d.

of the interest for 60d. To of the interest for 30d.

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60 days

=

93 days Now, since the interest of any sum at 6 per cent. for 2 months, or 60 days, equals of the principal (Art. 352), of $460 $4.60 will be the interest for 60 days; of the interest for 60 days, or $ 2.30, will be that for 30 days; and of the interest for 30 days, or $ 0.23, will be that for 3 days. The interest for the several parts of the time added together must give the interest for the whole time, or 93 days.

RULE. — Multiply the principal by the number denoting one sixth of the number of days expressed decimally as thousandths. Or,

Divide the principal by 100, and take such a part or parts of the quotient as the given number of days is of 60 days.

The result will be the interest at 6 per cent., from which it may be found for any other rate, as in Art. 355.

number of months of 30 Thus, one sixth of the

NOTE 1.- - One sixth of the number of days in any days each is equal to 5 times the number of months. number of days in 7 months equals 7 X 5, or 35 days; and one sixth of the number of days in 9 months and 13 days equals (9 × 5) + (13÷ 6), or 45 + 21 47 days.

=

60

365

NOTE 2. It is a common practice among mercantile men, in calculating interest, to consider a year to consist of only 360 days, but the laws of some of the States require 365 days to a year. 366 days are in fact only of a common year, and therefore are less than what perfect accuracy would require. Hence, when the year is considered to be one of 365 days, the interest as found by the rule must be diminished by principal by the number of days, and, if the if the rate be 7 PER CENT., divide by 5214 vide by 7300.

of itself; Or, we may multiply the rate be 6 PER CENT., divide by 60833; and if the rate be 5 PER CENT., di

EXAMPLES.

2. What is the interest of $96 for 33 days, at 7 per cent.? Ans. $.616. 3. What is the interest of $320.40 for 63 days, at 5 per cent.? Ans. $2.803.

4. What is the interest of $ 131.20 for 123 days?

Ans. $2.689.

5. What is the interest of $ 26.60 for 78 days? 6. What is the interest of $5780 for 153 days, at 10 per cent.? Ans. $245.65. 7. What is the interest of $105.10 for 48 days, at 12 per cent.? Ans. $1.681. 8. What is the interest of $13.62 for 93 days, at 7 per cent.?

9. What is the interest of $ 4580 for 253 days, at 5 per cent.? Ans. $177.02913. 10. What is the interest of $3140 for 273 days, at 7 per cent.? Ans. $166.6813. 11. What is the interest of $10550 for 243 days, at 8 per cent.? Ans. $569.70. 12. What is the amount of $33.44 for 333 days?

Ans. $35.295.

13. What is the amount of $71.60 for 3 months and 18 days?

14. What is the interest of $92.96 for 4 months and 3 days, at 7 per cent.? Ans. $2.223. 15. What is the interest of $144.50 for 144 days, allowing 365 days to the year, at 5 per cent.? Ans. $ 2.85. 16. What is the interest of $761.81 for 165 days, allowing 365 days to the year? Ans. $20.662.

17. What is the interest of $560 for 183 days, allowing 365 days to a year, at 7 per cent.? Ans. $19.65.

18. What is the interest of $1960 for 93 days? 19. What is the amount of $1000 for 1 month and 3 days? Ans. $1005.50. 20. What is the amount of $7300 for 18 days, at 6 per Ans. $7321.90.

cent.?

357. To find the interest on sterling money, at any rate per cent., for any time.

Ex. 1. What is the interest of 576£. 5s. 6d. for 1 year and

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We reduce the 5s. 6d. to the decimal of a pound (Art. 279), and annex it to the pounds; we then find the interest as though the sum expressed dollars and cents; and, reducing the decimal in the answer to shillings and pence, we have 63£. 7s. 9d.+ as the interest required. Hence,

Reduce the shillings, pence, and farthings, if any, in the principal to the decimal of a pound. Then proceed as in United States money; and, if there be a decimal in the result, reduce it to a compound number.

EXAMPLES.

2. What is the interest of 179£. 12s. 11d. for 1 year and 7 months, at 5 per cent.? Ans. 14£. 4s. 51d.

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3. What is the interest of 25£. for 1 year and 9 months, at per cent.?

4. What is the interest of 5440£. 10s. for 3 years and 11 months, at 6 per cent.? Ans. 1278£. 10s. 4d. 5. What is the interest of 943£. 1s. 8d. from May 1, 1857, to October 21, 1857, allowing 365 days to a year, at 54 per cent.? Ans. 23£. 9s. 4d.

358. To find the PRINCIPAL, the interest, the time, and the rate per cent. being given.

What principal will gain $120 in 4 years, at 6 per

Ex. 1. cent.?

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Ans. $500.

The interest for the given time and rate is 24 cents on a principal of $1; therefore,

the required principal will be as many times $1 as the number denoting the given interest contains times .24.

RULE.- ·Divide the given interest by the interest of $1 for the given time, at the given rate.

EXAMPLES.

2. What principal will gain $10.08 in 1 year, at 7 per cent.? Ans. $144. 3. What principal will yield an income of $13.20 in 1 year and 4 months, at 81 per cent.? Ans. $120. 4. What sum should be paid for a ground rent paying yearly, at 6 per cent., $ 40.50?

5. If the interest on a sum borrowed at 2 per cent. a month is $24 for 90 days, what is the sum? Ans. $400.

6. What principal at 7 per cent. is sufficient to produce $206.38 interest in 183 days? Ans. $5600.

359. To find the RATE PER CENT., the principal, the interest, and the time being given.

Ex. 1. If the interest of $500 for 4 years is $120, what is the rate per cent.?

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then the required rate will be as many per cent. as 20 is contained times in 120, or 6 per cent.

RULE. Divide the given interest by the interest of the given principal at 1 per cent. for the given time.

EXAMPLES.

2. The interest of $144 for 1 year is $ 10.08; what is the per cent.? Ans. 7 per cent.

rate

3. At what rate per cent. must $120 be on interest to amount to $133.20 in 1 year 4 months?

4. At what rate per cent. must $1, or any other sum, be on interest to double itself in 14 years? Ans. 7 per cent.

5. At what rate per cent. must any sum of money be on in

terest to quadruple itself in 33 years?

6. I receive yearly $232.50 interest on

the State of Massachusetts; what is the rate

Ans. 9 per cent.
$4650 loaned to
per cent.?

Ans. 5 per cent.

7. At what rate per cent. must $7500 be loaned to gain $60.00 in 48 days?

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