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:: SHORT RULES, “ FOR CASTING INTEREST AND REBATE;
POR FINDING THE CONTENTS OF SUPERFICIES, SOLIDS
SHORT RULES, FOR CASTING INTEREST AT SIX PER CENT. 1. To find the interest of any sum of shillings for any number of days less than a month, at 6 per cent.
RULE. 1. Multiply the shillings of the principal by the number of days, and that product by 2, and cut off three figures to the right hand, and all above three figures will be the interest in pence.
2. Multiply the figures cut off by 4, still striking off three figures to the right hand, and you will haye the farthings, very nearly.
Ans. 5d. 1,6qrs. 2. What is the interest of 211. 3s. for 29 days ? ?
E ARs. 2s. Od. 2grs.
FEDERAL MONEY. II. To find the interest of any number of cents for any number of days less than a month, at 6 per cent.
RULE. Multiply the cents by the number of days, divide the product bay 6, and point off two figures to the right, and all the figures at the left hand of the dash, will be the interest in mills, nearly.
EXAMPLES. Required the interest of 85 dollars, for 20 days. $ cts.
Ca m ills. , 85=8500X20-6=283,33 Ans. 283 which is
28 cts. 3 mills. 2. What is the interest of 73 dollars 41 cents, or 7341 cents, for 27 days, at 6 per cent. ?
Ans. ss0 mills, or 35 cts.
III. When the principal is given in pounds, shillings, &c.
New-England currency, to find the interest for any number of days, less than a month, in Federal Money.
RULE. - Multiply the shillings in the principal by the number of days, and divide the product by 36, the quotient will be the interest in mills, for the given time, nearly, omitting fractions.
EXAMPLE Required the interest, in Federal Money, of 271. 155. for 27 days, at 6 per cent. ;
£,. S. S. Ans. 27 15=555x27-36=416 mills, -41cts. 6m.
IV. When the principal is given in Federal Money, and
you want the interest in shillings, pence, &c. NewEngland currency, for any number of days less than a month.
RULE. PT... Multiply the principal, in cents, by the number of days,
and point off five figures to the right hand of the product, I which will give the interest for the given time, in shiltings and decimals of a shilling, very nearly.
EXAMPLES. A note for 65 dollars, 31 cents, has been on interest 25 days; how much is the interest thereof, in New-England currency?'. Scts...?
s. d.grs. Ans. 65,31=6531 X25=1,63275 =17 2 REMARKS.- In the above, and likewise in the preceding practical Rules, (page 127) the interest is confined at six per cent, which admits of a variety of short methods of casting; and when the rate of interest is 7 per cent. as established in New York, &c. you may first cast the interest at 6 per cent. and add thereto one sixth of itself, and the sum will be the interest ạt 7 per cent. which perhaps, many times, will be found more convenient than the general rule of casting interest. in
7,5 for 1 month.
A SHORT METHOD FOR FINDING THE REBATE OF ANY
EXAMPLES. 1. What is the rebate of 50 dollars for six months, at 8 per cent. !
$ cts. The interest of 50 dollars for 6 months, is 1 50 And, the interest of 1 dol. 50 cts. for 6 months, is 4.
Ans. Rebate, $1 46 , 2. What is the rebate of 1501. for 7 months, at 5 per cent.. aterest of 1501. for 7 months, is À 7 6 mterest of 41. 7s. 6d. for 7 months, is 2 61
Ans. 64 4 11f nearly. By the above Rule, those who use interest tables in their counting-houses, have only to deduct the interest of The interest, and the remainder is the discount.
A concise Rule to reduce the currencies of the different
States, where a dollar is an even number of shillings, to Federal Money.
RULE I. Bring the given sum into a decimal expression by inenection, (as in Problem I. page 87) then divide the whole by ,3 in New-England and by 4 in New-York currency, and the quotient will be dollars, cents, &c.
EXAMPLES. 1. Reduce 541. 8s. 31d. New-England currency, to Fedečal Money.
13)54,415 decimally expressed.
Ans. 8181,38 cts. 2. Reduce 7s. 113d. New-England currency, to Fede. med Money. 75. 118d.=£0,399 then; ,3),399
Ans: $1,33 3. Reduce 5131. 168. 10d. New-York, &c. currency, to Federal Money.
,4)513,842 decimal Ans. 91284,807
4. Reduce 19s. 534. New-York, &c. currency, to Federal Money,
94)0,974 decimal of 19s. 5Jd.
* 5. Reduce G4. New-England currency, to Federal
:: „3)64000 decimal expression.
8213,33} Ans. NOTE.By the foregoing rule you may carry on the decimal to any degree of exactness; but in ordinary practice, the following Contraction may be useful.
RULE II. To the shillings contained in the given sum, annex 8 times the given pence, increasing the product by 2; then divide the whole by the number of shillings contained in a dollar, and the quotient will be cents.
EXAMPLES 1. Reduce 45s. 60. New-England currency, to Fede. ral Money.
6x8+%= 50 to be annexed,
. Scts. $7.587 ins. 758 cents.-7,58 2. Re:luce 21. 20s. Id. New-York, &c. currency, to Feileral Money.
9x8+2=74 to be annescil. Then 8)5074
O r thus, 8)50,74
86,34 Ans. N. B. When there are no ience in the given sum, you must annex two cypliers to the shillings; then divide as belure, &c.
3. Reduce sl. ās. New-England currency, to Federal moncy. sl. 5s. =65s. Then 6)6500
Ans. 1083 cents.