The Principal is the sum lent.

*

The Rate is the premium per cent. agreed on."
The Amount is the sum of the principal and interest.
Interest is of two kinds, Simple and Compound.

SIMPLE INTEREST.

Simple Interest is that which is allowed on the Principal only. Note. By this Rule, Commission, Brokerage, Insurance, purchasing Stocks, or any thing else, rated at so much per cent. are calculated.

GENERAL RULE.

1. Multiply the Principal by the Rate, and divide by 100 (or cut off the two right hand figures in the Pounds) and the quotient, or left hand figures will be the answer in Pounds, &c. the right hand figures being reduced and cut off as at first. If the principal be dollars, the right hand figures will be cents.f

2. For more years than one, multiply the Interest of one year by the number of years.

3. For any number of months take the aliquot parts of a year; and for days, the aliquot parts of 30.

1. What is the interest of £573 13s. 91d. at 6 per cent. per annum? Ans. £34 8s. 5d.

*Lawful or legal interest is that which is permitted by the laws of the State. It is different under different governments. In England the Rate is five percent. In the New England States, it is sir, and, in the State of New York it is seven per cent. The courts of the United States allow interest according to the prac tice of the State where the suit was commenced. The rules of the Courts in the States of Massachusetts, Connecticut, and New York, for computing legal interest, will be given immediately before Discount,

† This rule is a contraction of a process in the Rule of Three. Thus in the

1st Example. As, 100 :: 6 : £573 13s. 94d.; the interest for a year. And 6X £573 138. 94d.

obvious.

100

£34 Es. 5d. the interest. The remainder of the rule is

The reason of the rule in the Note above is, that as 9 is 4 of 12 months, if the rate be 9 per cent, multiply the principal by of the months; if the rate he 8 per cent. by 3 of the number of months; and if 6, by half the months, ke.

£573 13 9

6

£34-42 2 9
20

8.42

12

5.13

4

.52

2. What is the interest of £329 175. 6d. for 3 years, 7 months, and 12 days, at 5 per cent. per annum. Ans. £59 13s.

£329 17 6d.

5 6 mons.

16.49 7 81

20

1 mon.

Then,

8 4 11 do. of

6 months

10.52

3. What is the interest of 347 dollars 50 cents, at 6 per cent.

per annum for a year.

$347.50 Or $100: 6: 347.50c.: $20 85c.

6

20.8500 Ans. $20 85c.

4. What is the interest of $797 13c. at 6 per cent. per annum,

for 8 months?

$797:13

4

31.8852

Ans. $31 88c. 5,2m.

5. What is the interest of $649 17c. at 6 per cent. per annum, for 15 months?

Ans. $48 68c. 73m.

6. Required the amount of £725 12s. 6d. at 5 per cent. per annum, for a year?

5725 12 6

36 57

Ans. £761 18 11

7. What is the amount of $560 50c. at 6 per cent. for 16 months?

$560 50

8

44.84

560.50

Ans. $605.34c.

3. What is the interest of $150 75c. for 1 month, at 6 per cent. per annum?

150.75

.75375 Ans. 75cts. 33 mills.

So that any number of dollars, considered as so many cents, is the interest for 2 months, at 6 per cent. and the half of it is the monthly interest.

COMMISSION, OR FACTORAGE,

Is an allowance of so much per cent. to a Factor or Correspondent, for buying and selling goods.

9. Required the commission on £436 9s. 6d. at 31 per cent.

£436 9 6

31

1309 8 6

218 4 9

15-27 13 3

20

5.53

12

6.39

4

1.56 Ans. £15 5 6).

10. Required the commission on $649 75c. at 1 per cent.

649.75
324.875

162-4375

1137-0625 Ans. $11 37c. 0 in.

BROKERAGE

Is an allowance of so much per cent. to a person called a Broker, for assisting merchants in purchasing or selling goods. 11. Required the Brokerage on £911 12s. at 5s. or per cent. 5s.1911 12

3.84

12. Required the Brokerage on $876 21c. at 33 cents, or at per cent.

1876-21

292-07 Ans. $2 92c. 0 m.

BUYING AND SELLING STOCKS.

Stock is a general name for the capitals of trading companies, or, of a fund established by government, the value of which is variable

13. Required the amount of £375 15s. bank stock, at £75 per cent ?

504375 15

25 187 17 6

93 18 9

Ans. £281 16 3

Or thus: 25375 15 Subtract 93 18 9

As before, £281 16 3

14. Required the amount of $2195 50c. bank stock, at 125 per

cent.

2542195-50

Add 548-875

Ans. $2744 375

15. What is the value of $6950 at 105 per cent?

Ans. $7297 50cts.

16. Value of £225 of stock at 95 per cent.? Ans. £213 15s.

Multiply the principal by the days, and that product by the rate, and divide the last product by 365×100.*

15. Required the interest of £360 10s. for 175

cent.

360.5X175X6

100X365

£10-17

days, at 6 per

£10 7s. 42d.

Rule for making a divisor for any Rate.

Multiply 365 by 100, and divide by the rate. Thus, for 6 per

365×100

=6083 divisor.

*This rule is the result of a statement in the Double Rule of Three, as follows.

£ Rate. Prin.

As 100
Days.

And as 365 :

to the Rule we have

6: 360-5: the interest for 1 year.

Days.

:: 175: the interest for 175 days. Wrought according 360.5 X 175 X6

The rule for finding a divisor for any Rate, is a contraction of this result. 360-5X175X6

are formed for any other rate. Hence too, the 2d Rule is obvious, for

360-5X175 6083

the interest, and is the product of the principal and days divided by the divisor formed as above.

When the time is given in months, the divisor is formed in a similar manner. Suppose in the last example the time had been 11 months. Then,

As 100 6: 360-5: the interest for a year, and as 12: :: 11 months: the inter360-5X11X6 12X100

Note. As 365 days: 5 per cent. :: 7300 days: 100 per cent. And as 12 months: 5 per cent. :: 240 months: 100 per cent. Hence it is evident that if the Rate be 5, any principal will gain 100 per cent. that is, will double in 7300 days or 240 months. And at 6 per cent. any sum will double in 6083 days, or 200 months, and at 7 per cent. in 52142 days, or 1712 months.