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IV. When the principal is given in pounds, shillings, &c. New-England currency, at 6 per cent. to find how much the monthly interest will be in lederal money.
RULE.. Multiply the pounis, &c. by 5, and divile that product by S, the quotient will be the interest for one mo:ith, in cents, and decimals of a cent, &c.
EXAMPLES. 1. A note for £411 New-England currency has been on interest one month; how much is the interest thereof in federal money. :
Ans. 685ets. 86, 85cts. 9. Required the interest of 39.185. N. E, currency foi 7 nionths
30,9 decimal value.
3) 199,5 Interest for 1 mo. 66,5 ccnts.
Hitta for 7 months, 465,5cts:=:84, 65cts. 5m. Ans.
1. When the principal is given in New-löngland and Virginia .currency, at 6 per cent. to find the interest for a ycar, in dollars, cents and mills, by inspection.
RULE. Since the interest of a rear wil lor just so many cents as the given poincinal contains shillings, therefore, write down the sliiliings arid raid tiem cents, and tlie pence in the principal maile less isv 1. if they exceed 3, or by 2 when they exceed 9, will be the nills, very nearly.
VI. To compute the interest on any note or obligation when there are payments in part, or indorsements.
ROLE. 1. Find the amount of tie whole principal for the whole time.
2. Cast the interest on the several payments, from the time they were paid, to the time of seriement, and find heir amunt; and lastly deluci the amount of the seveGal payments, from the amount of the principal.
EXAMPLES. Suppose a bond or note slated April 17,1793, was given for 625 dollars, interest at 6 per cent. and there were payments indorsed upon it as follows, viz..
Firsi payment. 148 dollars, May 1, 1734.
Third paviment, 99 dols. Jau.2, 1798. Irenand how much remains due on said note, the 17th of June, 1798 :
8 ots. 148, 00 first payment, Mav 7, 1794. Ir. mo 56, 50 interest up to June 17, 1798.=4 15
181, 50 amount.
341, 00 second payment, Aug. 17, 1796. Ir.no, 37, 51 Interesi timama June 17 1798. = 10
$78, 51 amount.
8219, 52 remains due on the note, June 17, 1798.
2. On the 16th of January, 1795, I lent James Paywell 500 dollars, on interest at 6 per ceut. which I received back in the following partial payments, as under, viz.
1st of April, 1796 -' . . - $ 50
. 60 How stands the balance between us, on the 16th No. vember, 1800 ?
Ars. due to me 863, 18cts. 3. A PROMISORY NOTE, viz. 662 10s.
New-London, April 4, 1797. On demand I promise to pay Timothy Careful, sixtytwo pounds, ten shillings, and interest at 6 per cento per annum, till paid; value received. John STANBY,
PETER PAYWELL. RICHARD TESTIS.
Indorsements. . 6. S. 1st. Received in part of the above note, Sep- . tember 4, 1799.
500 And payment June 4, 1800,
12 10 How much remains due on said note. the fourth day of December, 1800 ?
NOTE.—The preceding Rule, by custom is rendered so popular, and so much practised and esteemed by many on account of its being simple and concise, that I have given it a place: it may answer for short periods of time, but in a long course of years, it will be found to be very errone. ous.
Although this method seems at first view to be upon the ground of simple interest, yet upon a little attention the following objection will be found most clearly to lie against it, viz. that the interest will, in a course of years, com pletely expunge, or as it may be said, eat up the debt. For an explanation of this, take the following
A lends B 100 dollars, at 6 per cent. interest, and takes his note of hand; B does no more than pay A at every year's end 6 dollars, (which is then justly due to B for the use of his money) and has it endorsed on his note. At the end of 10 years B takes up his note, and the sum he has to pay is reconed thus : The principal 100 dollars, on interest 10 years amounts to 160 dollars ; there are nine endorsements of 6 dollars each, upon which the debtor claims interest; one for 9 years, the second for 8 years, the third for 7 years, and so down to the time of settlement; the whole amount of the several endorsements and their interests, (as any one may see by casting it) is $70, 20 cts. this subtracted from 180 dols. the amount of the debt, leaves in favor of the creditor, 889,40 cts. or 810, 20 cts. less than the original principal, of which he has not received a cent, but only its annual interest.
If the same note should lie 20 years in the same way B would owe but 37 dols. 60 cts. without paying the least fraction of the 100 dollars borrowed.
Extend it to 28 years, and A the creditor would fall in debt to B, without receiving a cent of the 100 dollars which he lent him. See a better Rule in Simple Interest nog decimals, page 175.
COMPOUND INTEREST, IS when the interest is added to the principal, at the end ul the year, and on that amount the interest cast for anoth or year, and allied again, and so on : this is called Inter est upou Interest.
RULE. Find the interest for a year, and and it to the principai, which call the amount from the first sear; find tlic interes! of this amount, which add as beture, for the amount of the srcond, and so on for any number of years requiredi. Sibtract the original prin inal from the last amounit, and the remainder will be the Compound Interest for the whole time.
EXAMPLES. 1. Required the amount of :00 dollars for 3 years at 6 per ceat. per annani, compound interesti S otse
8 ots. 1st Principal 100,00 Amount 100.00 for 1 rear. 2. Principal 106,00 An:ount 112,16 for 2 years. Sd Principiil 112,30 Amount 119.1016 for yrs. Ans.
2. What is the amount of 425 duitars, fur t years, at 5 per cent. per annuill, compound interest i
Ans. 8516, 59cts. s. What will 4001. amount to, in 4 yrars, at 6 per cento per annull, compouni interest i wos: 4.504 198. 9jd.
4. What is the compound interest of 1501. 108. Boxe 3 years, at 6 per ct, per antaum: Aus. £28 143. 11 fel. +
5. What is the coinpound interest of 300 dollars for 4 years, at 6 per cent. per annum : Anis, 8131.38+
6. What will 1000 doilars amount to in 4 years, at 7 per cent per annum, compuuni interest:
ins. 81310, 79r1s. Em.t 7. What is the amount of :50 dollars fut 4 years, at 6 per cent. per annun, compund interest :
rs. $946, 83618. :,:2), 8. What is the ca npound interest of 876 Juls. 90 cta far 35 years, at 6 per cento per annuiu :
Ana $128, licts +