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6. What is the interest of $35.31 for 1 year, at 6 per cent. ?

7. What is the interest of $50.10 for 1 year, at 7 per cent. ?

8. What is the interest of $63 for 1 year, at 5 per cent. ?

9. What is the interest of $136.75 for 1 year, at 41⁄2 per cent. ?

10. What is the interest of $260.61 for 1 year, at 6 per cent. ? What is the amount?

Ans. $15.636 int. $276.246 amount. (Art. 237. Obs. 2.) 11. What is the interest of $140.25 for 1 year, at 7 per cent.? The amount?

12. What is the interest of $163.40 for one year, at 8 per cent.? The amount?

13. What is the interest of $400 for 1 year, at 6 per cent.? The amount?

14. What is the amount of $500 for 1 year, at 7 per cent. ?

15. What is the amount of $1000 for 1 year, at 8 per cent.?

16. What is the interest of $100 for 3 years, at 6 per cent. per annum?

Operation.
$100 Prin.

.06 Rate.

$6.00 Int. 1 y. 3 No. of y. $18.00 Int. for 3 y.

The interest for 3 years is plainly 3 times as much as for 1 year. We therefore first find the interest for 1 year as above, which is $6; then multiplying this by 3, gives the interest for 3 years. Hence,

238. To compute the interest of any sum for a given number of years.

First find the interest of the given sum for 1 year, at the given rate; (Art. 237;) then multiply the interest of 1 year by the given number of years.

QUEST.-238. How is interest computed for any number of years?

17. At 5 per cent. per annum, what is the interest of $45 for 4 years? Ans. $9.

18. At 6 per cent., what is the interest of $200 for 5 years ? What the amount?

19. At 7 per cent., what is the interest of $250 for 10 years? What the amount?

20. At 8 per cent., what is the interest of $340.50 for 3 years? What the amount?

21. At 6 per cent. per annum, what is the interest of $100 for 1 month?

Operation.
$100 Prin.

.06 Rate.

12)6.00 Int. for 1 y.

$.50 Int. for 1 m.

1 month is of 12 months or a year, therefore the interest for 1 month will be

as much

as the interest for 1 year. Now the interest of $100 for 1 year is $6, and of $6 is 50 cts. In like manner any number of months may be considered a fractional part of a year, and the interest for them may be computed in the same way.

Hence,

239. To compute the interest of any sum for a given number of months.

First find the interest for 1 year as above; then take such a fractional part of 1 year's interest, as is denoted by the given number of months.

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Thus for 1 month take of 1 year's interest; for 2 months, or for 3 months, or ; for 4 months, 12 or; for 6 months, 12 or ; &c.

22. At 5 per cent., what is the interest of $600 for 6 months? Ans. $15.

23. At 7 per cent., what is the interest of $250 for 4 months?

QUEST.-239. How is interest computed for months? For 2 months, what part would you take? For 3 months? 4 months? 5 months? 6 months? 7 months? 8 months? 9 months? 10 months? 11 months?

24. What is the interest of $375.31 for 3 months, at 6 per cent. ?

25. What is the interest of $60 for 7 months, at 8 per cent.? What is the amount?

26. What is the interest of $96 for 10 months, at 6 per cent.? What is the amount?

27. At 6 per cent., what is the interest of $600 for 1

day?

Operation.
$600 Prin.

.06 Rate.

1 day is of 30 days, or a month; hence the interest for 1 day will be of the interest for 1 month. If,

12)$36.00 In. for 1 y. therefore, we find the inter30)3.00 In. for 1 m. est for 1 month, and take Ans. $0.10 In. for 1 d. of this, it will evidently be the interest for 1 day. In like manner, any number of days may be considered a fractional part of a month, and the interest for them may be found in the same way Hence,

240. To compute the interest of any sum for a given number of days.

of

First find the interest for 1 month as above, then take such a fractional part of 1 month's interest as is denoted by the given number of days. Thus for 1 day take I month's interest; for 2 days, 3, or 15; for 3 days, 30, oro; for 10 days,; for 20 days, ; &c.

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28. At 4 per cent., what is the interest of $470 for 10 days? Ans. $0.522.

29. What is the interest of $1000 for 1 y. 1 m. and 1 d., at 6 per cent.?

30. What is the interest of $42.50 for 2 years and 6 months, at 7 per cent. ?

31. What is the interest of $69.46 for 1 year and 8 months, at 8 per cent.?

QUEST.-240. How is interest computed for days? For 2 days, what part would you take? For 5 days? 7 days? 12 days? 25 days?

241. From the foregoing principles we may deduce the following

GENERAL RULE FOR COMPUTING INTEREST.

I. FOR ONE YEAR. Multiply the principal by the given rate, and from the product point off as many figures for decimals, as there are decimal places in both factors. (Art. 237.)

II. FOR TWO OR MORE YEARS. Multiply the interest of 1 year by the given number of years. (Art. 238.)

III. FOR MONTHS. Take such a fractional part of 1 year's interest, as is denoted by the given number of months. (Art. 239.)

IV. FOR DAYS. Take such a fractional part of 1 month's interest, as is denoted by the given number of days.

OBS. 1. In calculating interest for months, a month, whether it contains 30 or 31 days, or even but 28 or 29, as in the case of February, is always assumed to be one twelfth of a year.

2. In calculating interest for days, 30 days are considered a month; consequently the interest for 1 day, or any number of days under 30, is so many thirtieths of a month's interest. (Art. 170. Obs. 2.)

This practice seems to have been originally adopted on account of its convenience. Though not strictly accurate, it is sanctioned by custom, and is everywhere allowed by law.

32. What is the interest of $45.23 for 1 year and 2 months, at 5 per cent.?

33. What is the interest of $43.01 for 21 years, at 7 per cent.?

34. What is the interest of $215.135 for 2 years and 3 months, at 6 per cent.?

35. At 8 per cent., what is the interest of $75.98 for 3 years?

36. At 5 per cent., what is the interest of $939 for 4 years?

37. At 6 per cent., what is the interest of $137.50 for 6 months?

QUEST.-241. What is the general rule for computing interest? Obs. In reckoning interest, what part of a year is a month considered? How many days are considered a month? Is this practice strictly accurate?

38. At 7 per cent, what is the interest of $1500 for 10 days?

39. At 20 per cent., what is the interest of $3000 for 3 days?

40. At 12 per cent., what is the interest of $1736.25 for 6 months?

SECOND METHOD OF COMPUTING INTEREST.

242. There is another method of computing interest, which is very simple and convenient in its application, particularly when the interest is required for months and days at 6 per cent.

INTEREST OF $1 FOR MONTHS.

243. We have seen, (Art. 237,) that,

For 1 year, the interest of $1 is

6 cents, which is $.06;

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That is, the interest of $1 for 1 month, at 6 per cent., is 5 mills; and for every 2 months, it is 1 cent, &c. Hence,

244. To find the interest of $1 for any number of months, at 6 per cent.

Multiply the interest of $1 for 1 month, ($.005,) by the given number of months, and point off 3 decimal figures in the product. (Art. 191.)

1. At 6 per cent., what is the interest of $1 for 7 months?

QUEST.-244. How may the interest of $1 be found for any number of months, at 6 per cent.?

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