5 months, and 25 days, at 6L. per cent. per annum? Ans. 6L. 6s. 10d.

10. What is the amount of a bond for 967 dollars, for 2 years and 4 months, at 6 dollars per cent. per annum? Ans. 1102.38. 11. What is the amount of 100L. for 18 months, at 8 per cent. per annum?

Ans. 12L.

Note. The answers to the following questions may be found by the concise method at the bottom of the page: but it is thought best that the learner should first obtain them by the preceding general rule. *

12. What is the interest of 900L. for 8 months, at Ans. 36L.

6L. per cent. per annum?

13. What is the interest of 450L. for 4 months, at Ans. 10L. 10s.

7L. per cent. per annum?

14. What is the interest of 148L. 12s. 6d. for 11 months, at 6 per cent. per annum? Ans. 8L. 3s. 54d. 15. What is is t the interest of 1260 dollars for 4 months, at 6 dollars per cent. per annum; and also at 7 per cent. per annum?

$25.20 interest at 6 per cent. $29.40 interest at 7 per cent.

* The interest of any sum for any number of months, may be concisely found by the following method.

Multiply the principal by half the number of months, and divide the product by 100; or multiply the principal by the whole number of months, divide the product by 2, and divide the quotient by 100: the result of either operation will be the interest at 6 per cent. per annum.

For the interest at any other rate per cent. take aliquot parts of the interest at 6 per cent, and add, or subtract, as the case requires.

EXAMPLE.

What is the interest of 450L. for 8 months, at 6L. per cent. per annum; and also at 7L. per cent. per annum?

16. What is the interest of 630 dollars for 8 months, Ans. $25.20.

at 6 dollars per cent. per annum?

17. What is the interest of 7342 dollars for 16 months,

at 6 dollars per cent. per annum?

Ans. $587.36.

18. What is the interest of 750 dollars for 9 months,

at 7 dollars per cent. per annum?

Ans. $39.37.

19. What is the interest of 375 dollars for 5 months, at 6 dollars per cent. per annum? Ans. $10.314. * 20. What is the interest of $460.50 for 4 months,

at 6 dollars per cent. per annum.

Ans. $9.21.

Ans. $10.74.

21. What is the interest of $230.25 for 8 months, at 7 dollars per cent. per annum? 22. What is the interest of $764.50 for 3 years and 10 months, at 6 dollars per cent. per annum?

Ans. $175.83.

To find the interest of any given sum as computed at the banks, at 6 per cent.

RULE.

1. Multiply the dollars by the number of days, and divide the product by 6; the quotient will be the interest in mills. Or,

2. If the principal be any number of dollars, the interest for 60 days, at 6 per cent. will be exactly that

* When the principal consists of dollars and cents, the interest may be found thus:

Reduce the principal to cents, by removing the separating point: then multiply and divide as directed in the last note, and separate one figure from the right of the result as a remainder or fraction; the figures on the left of this will be the interest in mills.

EXAMPLE.

What is the interest of $425.98 for 3 months, at 6 dollars per cent. per annum? and also at 7 dollars per cent. per annum?

number of cents: and for the time more or less than 60

take aliquot parts. *

EXAMPLES.

1. What is the interest of 1542 dollars for 90 days, at 6 per cent. per annum? also, for 60,t for 30, and for 20 days, at the same rate?

Dols.

301542 int. for 60 days in cents.

2. What is the interest of 771 dollars for 90 days, at

Ans. $11.56.

3. What is the interest of 3084 dollars for 30 days,

6 per cent. per annum?

at 6 per cent. per annum?

Ans. $15.42.

4. What is the interest of 2324 dollars for 54 days,

at 6 per cent. per annum?

Ans. $20.91

5. What is the interest of 3942 dollars for 50 days,

at 6 per cent. per annum?

CASE 5.

Ans. $32.85.

To find the principal, when the amount, time, and rate per cent. are given.

RULE.

Find the amount of 100 pounds, or dollars, at the

rate and time given: then,

As the amount of 100 pounds, or dollars,

Is to the amount given,

So are 100 pounds, or dollars,

To the principal required.

* This is calculating after the rate of 360 instead of 365 days to the year, which will always make the interest rather too much.

If the interest found by this rule be divided by 73, the quotient will show by how much it exceeds the true interest.

† When a note is drawn for 60 days, the interest is mostly calculated for 63, on account of three days called days of grace, which are commonly allowed the payer, on all notes, after the time expires for which they are drawn. The interest is here only computed for the given time.

EXAMPLES.

1. What principal at interest for five years, at 6 per

cent. per annum, will amount to 650L.?

L.

6

5 years

30 int. of 100L. for 5 years

100

Ans. 500L.

00

130 amt. of 100L. for 5 years. 2. What principal at interest for 10 years, at 6 per cent. per annum, will amount to 1300L.?

Ans. 812L. 10s.

3. What principal at interest for 4 years, at 5 per cent. per annum, will amount to $571.20?

CASE 6.

Ans. 476 dollars.

To find the rate per cent. when the amount, time and

principal are given.

RULE.

Subtract the principal from the amount, and the remainder will be the interest for the given time: then,

As the principal,

Is to one hundred pounds or dollars,

So is the interest of the principal, for the given time, To the interest of 100 pounds, or dollars, for the

same time:

Again,

As the given time,

Is to one year,

So is the interest last found,

To the rate per cent. required.

EXAMPLES.

1. At what rate per cent. per annum, will 500L.

amount to 650L. in 5 years?

Ans. 6L. per cent.

150 Int. for the given time. 5": 1 ::

2. At what rate per cent. per annum, will 500L. amount to 725L. in 9 years? Ans. 5L. per cent.

amount to 856dols. 50cts. in 9 years and 6 months?

CASE 7.

Ans. 41⁄2 per cent.

To find the time, when the principal, amount, and rate per cent. are given.

RULE.

Find the interest of the principal for one year.

Find the interest for the time required, by subtract

ing the principal from the amount: then,

As the interest of the principal for one year,

Is to the interest for the time required,

So is one year,

To the time required.

EXAMPLES.

1. In what will time 500L. amount to 725L. at 5 per

cent. per annum?

L. 25/00

per cent. per annum?

lars, at 6 per cent. per annum?

225 Interest for time required.

2. In what time will 540L. amount to 734L. 8s. at 4

3. In what time will 600 dollars amount to 798 dol

Ans. 9 years.

Ans. 5 years.

INSURANCE, COMMISSION, AND BROKAGE,

Insurance, Commission, and Brokage, are allowances made to insurers, factors, and brokers, at a stipulated rate per cent.

RULE.

Work as if to find the interest of the given sum for one year, at the proposed rate: or, if the rate be less