Page images
PDF
EPUB

EXAMPLE FOR ILLUSTRATION.

1, What principal, being put out to Interest for 7 years, at 5

per cent. will amount to 270/?
1、
1.
1,
100 as 135: 100 :: 270

1,

Ans, 2001.

5

500

7

35.00

100

135 1,

100

I found the amount of

100l, at the rate and time

135)2700(200given; which was 135l, and

270

then stated it according to

rule; saying, if 135l, amount

[blocks in formation]

2. What principal, being put out to interest for 5 years at 6 Ans, 800 dollars,

per cent, will amount to 1040 dollars?

Find the amount of 100 dollars, and proceed according to rule.

CASE VIII.

When the principal, amount and time are given, to find the rate per cent,

RULE.

Find the interest for the whole time; this is done by subtracting the principal from the amount; the remainder is the interest for the whole time, Then say, as the principal is to the interest thus found, so is 100l, or 100 dollars, to the interest for the same time,

Lastly, divide the interest found by the given time, and the quotient will be the rate per cent. required.

EXAMPLE FOR ILLUSTRATION.

1. At what rate per cent. per annum, will 800 dollars amount Ans. 6 dolls, per cent.

[blocks in formation]

2. At what rate per cent. per annum, will 200l, amount to

270l, in 7 years?

CASE IX.

Ans. 5 per cent,

When the principal, rate per cent, and amount are given, to find the time,

RULE.

Find the interest of the principal for 1 year; also, find the whole interest as in the last case, Then say, as the interest of the principal for 1 year is to 1 year, so is the whole interest to the time required,

EXAMPLE FOR ILLUSTRATION.

1. In what time will 200l. amount to 270l. at 5 per cent. per

annum?

[blocks in formation]

Ans, 7 years,

As directed in the rule, I found the interest of the principal for 1 year; then I found the whole interest as in the last case; after this was done, I stated it according to rule, &c.

2. In what time will $800 amount to $1040 at 6 per cent. per annum? Ans, 5 years. For several methods of computing interest on notes, having endorsements. See Simple Interest, by Decimals,

COMPOUND INTEREST.

Compound Interest is interest upon interest, or it is that which arises from the interest being added to the principal, and, continuing in the hands of the borrower, becomes a part of the principal at the end of the stated time of payment, Thus, if 100 dollars be put out on interest, at 6 per cent, per annum, at the end of a year, there is 106 dollars, due the lender; this 106 dollars is the principal for the second year to draw interest, and so on,

RULE.

Find the amount of the principal for the first year by Simple Interest, and this amount will be a new principal for the second year. Find the amount of this new principal as before, and this amount will be the principal for the third year, &c. which will appear plain, from what follows, Suppose 100 dollars be reckoned at Compound Interest, at 6 per cent. per annum. The amount of this, for 1 year, is 106 dollars, which is the principal for the second year. The amount of 106 dollars is 112 dollars, 36 cents; this is the principal for the third year, &c.

Note, Subtract the given principal from the last amount; the remainder will be the Compound Interest,

EXAMPLE FOR ILLUSTRATION.

1. What is the amount of 220l. for 3 years, at 6 per cent, per annum, Compound Interest?

[blocks in formation]

Ans. 2621. Os. 5d. 2qrs.

1.

S. d. 233 4 0 new prin. or thus, 220 13 19 10 interest,

247 3 10 2d year.

6

114.83 3 0

6

13.20

220.

233.20

[blocks in formation]

20

s 16.63

12

233 4 amt. 1st yr. 7.56

6

13.99.20

[blocks in formation]

233.20.

247.19.20

6

14.83.15.20

247.19.20.

0 new prin.

1. 262.0235.20

12

14 16 7 2 interest.

20

[blocks in formation]

Work out this question and examine it, before you proceed to the

t.

EXAMPLES.

2. What is the amount of $350 for 4 years, at 4 per cent.

per annum. at Compound Interest?

Ans. $409. 45cts.+

By a careful attention to the rule, and the first example, you may get along with these questions.

3. What is the amount of £300 for 3 years, at 5 per cent. Ans, £3475s. 9d.

per annum. at Compound Interest?

4. What is the compound interest of $400 for 5 years, at 6 per cent. per annum? Ans. 135D. 29cts.+

Proceed to find the amount as before; then, to find the compound interest, go according to the note given under the rule.

Observe-When the interest is required for months, or for months and days, besides years-find the interest for one year more than the given number of years; and from that year's interest find the interest for the odd time more than the years - given in the question; add the interest thus found to the last amount; the sum will be the amount required.

Promiscuous Examples for Exercise in Interest, &c.

1, What is the amount of 445D, for 5 months and 11 days, at 6 per cent. per annum.? Ans. 456D. 94cts.

Find the interest for one year; then say, 4 months is the - of a year; 1 month is the - of 4 months; then, 10 days is the of 1 month, and 1 day is the of 10 days.

2. What is the interest of 333D. 42cts, for 13 years, at 6 Ans. 37D. 92cts. 6m.+

per cent. per annum.?

Case 3, Simple Interest.

3. What is the amount of 269D. 94cts. for 3 years, and 10

months, at 5 per cent per annum?

Ans. 321D. 67cts. 8m.+

When you take parts for the 10 mo. say 6 mo. is the - of a year, &c. 4. What is the interest of 948D. for 232 days, at 6 per cent. per annum? Ans. 36D. 15cts. 3m. + 5. What is the insurance on a store of goods, valued at 3260D. at, or 75 per cent. Ans. 24D. 45cts. 6. What will the commission on 1268D. 60cts. come to, at 11 per cent? Ans. 15D. 85cts. 7m. +

7. What is the amount of a note, given for 239D. 42cts. that has been standing 4 years, at 6 per cent. per annum?

Ans. 296D, 88cts.+ 8. What is the interest of 948D. 94.cts for 28 weeks, at 5 per cent. per annum? Ans. 25D. 54.cts. 8m.+ 9. What may a broker demand for the sale of goods to the

amount of 2246D. at 13 per cent? Ans. 39D.30.cts.5m. 10. What is the amount of 225D.50cts. for 4 years, at 6 per cent, compound interest? Ans. 284D. 68cts. 8m.

REBATE OR DISCOUNT.

REBATE, OR DISCOUNT, is a deduction or an allowance, made for the payment of any sum of money before it is due; or, it is a deduction made upon advancing the ready money for notes, bills, &c. which are due, or to be paid at some future day, Thus, suppose you purchase a quantity of goods and give your note for the same, to be paid 6 months from the date. If you pay the money before the time expires, the person holding the note makes a deduction for present payment, at some rate per cent. agreed upon for the time yet to come; and it is evidently right he should, as he would have the use of the money before it was due; this deduction is called the Rebate, or Discount; and what remains after the discount is deducted, is the present worth; and is such a sum, that, being put to interest, would amount to the given sum or debt, at the rate and time given.

RULE.

Find the amount of £100 or $100, at the given rate and time; that is, find the interest, and add it to the 100l. or 100 dollars; then state it as follows:

As the amount found, as above, is to the interest of £100 or 100 dollars first found, so is the given sum to the discount. Subtract the discount thus found from the given sum; the remainder will be the present worth. Or,

As the amount of £100 or 100D. is to the 100, so is the given sum to the present worth.

PROOF.

Find the amount of the present worth at the given rate and time, and, if the work is right, it will be equal to the given sum.

EXAMPLES FOR ILLUSTRATION.

1. What is the discount on a note, given for 106D. due 1 year

hence, at 6 per cent?

[blocks in formation]

Ans. 6 dollars.

Here you will see, that, on a note due 1 year hence, there is 6 dollars for present payment; so by paying 100 dolls down, the debt of 106 dollars, due one year hence, is discharged. It needs nothing more said, to prove

« PreviousContinue »