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Multiply the principal, in cents, by the number of days, and o off five figures to the right hand of the product, which will give the interest for the given time, in shiilings and decimals of a shilling, very nearly.
ExA.M to I, I.S.
A note for 65 dollars, 31 cents, has been on interest 25
days; how much is the interest thereof, in New-England currency P S cłs. S. S. d. Jrs. ..?ns. 65,31 ==6531 ×25–1,63375 = i. 7 o'
REMARKs.—In the above, and likewise in the preceding practical Rules, (page 12Y) the interestis 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 at 7 per cent. which perhaps, many times, will be found more convenient than the general rule of casting interest.
EXA M PH, E,
Required the interest of 75l. for 5 months at 7 per
a 5 hi(, RT METHOD FOR FINDING THE REBATE OF ANY" CIvi. N sums, FoR Mox Tris AND DAYs. U}.E. Dimitish the interest of the given sum for the time by its own interest, and this gives the Rebate very nearly. EXAMPI.E.S. 3. What is the rebate of 50 dollars for six months, at
S cts. The interest of 50 dollars for a months, is 1 50 And, the interest of I dol. 50 cts. Tur 6 months, is
ns. Bphate, SI 2. What is the rebate of 150!. for 7 months, at 5 per cont. ?
Intercy of 150!. for 7 months, is 4 7 6
Ans: £,4 4 113 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 lule to reduce the currencies of the different
States, where a dollar is an even number of shillings, to Federui Ioney.
RULE I. Bring the given sum into a decimal expression by in spection. (is in Problem I. page 87) then divide the wirula by ,s in New-England and by ,4 in New-York currency, and the quotient will be dollars, cents, &c.
1. Reduce 541. Es. Sid. New-England currency, to Federal Mouey.
,3)51,415 decimally expressed.
Ans. $181,58 cts. 2. Reduce 7s. 11d. New-England currency, to Fede. ral Money. 7s. 118!.=£0,399 then, ,3),399
Ans. $1,35 3. Reiluce 5151. 16s. 10d. New-York, &c. currency to Federal Money.
$2,43% .1ms. 5. Reduce 64!. New-England currency, to Federal Money. t ,3)64000 decimal expression.
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.
H.UH.E II. To the shillings contained in the given sum, annex b 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.
N. B. When there are no pence in the given sum, you must annex two cyphers to the shillings; then divide as before, &c.
3. Reduce Sl. 5s. New-England currency, to Federal
cents, 1083 Ams
VOR FIXDISG THE CONTEXTS 02 SUPERFICIES
SOLI!S. SECTION I. OF SUPERFICIES. The superficies or area of any plane surface, is composed or made
up Squares, either greater or less, according to the different measures by which the aimensions of the figure are taken or ineasured :--and because 12 inches in length make i foot of long measure, thereCore, 12x12=144, the square inches in a superficiai foot, &c.
Art. l. To find the area of a square having equal sitles.
RULE. Multiply the side of the square into itself, and the product will be the area, or content.
1. Ilow many squire feet of bearils are contained in the floor of a room which is 20 feet square ?
20x20=200 feet, the Answ'?r. 2. Suppose a square lot of land measures 26 rods on rach side, how many acres doth it contain:
Nore.---160 square rods make an acre.
56:. the usuer. ART. 2. To measure a Parallelorum, or long square.
Draultiply the lengti by the breadil, and the product will be the area or superficial content.
1. A certain garden, in form of a long squwe, is 96 ft. long, and 54 wide; how many square feet of ground are contained in it? Ins. 96X545519 4 square feet.
2. A lot of land, in form of a long squarc, is 120 rods m length, and to reds wide ; how many acres are in it?
120x60=7200 sip. rods, then?, 1200 = 45 cores, ins. 3. If a board or plank be 21 fcet long; and 18 inches how
many square feet are contained in it? 18 inches 1,5 trial, then 21X1,5=31,5 Ins.
Or, in measuring boards, yoriy multiply the length iu feet by the breadth ja inc!:es, and divide by 12, the quotient will give the answer in square feet, &c.
Thus, in the foregoing example, 21X18+12=31,5 as before.
4. If a board le 6 inches wide, how much in length will inake a square foot ?
RULE.--Divide 144 by the breacith, thus, 8)144
Ans. 18 in. 5. If a piece of land lie 5 rods wide, how many rous in length will make an acre ?
RULE.---Divide 160 by the breadth, and the quotient will be the length required, thus, 5)100
Ans. $2 rods in length. ART. 3. To measure a Triangle. Definition.- Triangle is any three cornered figure which is bounded by three right lines.*
RULE. Multiply the base of the given triangle into half its perpendicular height, or half the base into the whole perpendicular, and the product will be the area.
1. Required the area of a triangle whose base or long. est side is S2 inches, and the perpendicular height 14 inches. 52x7=224 square inches, the Answer.
2. There is a triangular or three cornered lot of land whose base or longest side is 51 rods; the perpendicular from the corner opposite the base, measures 44 rods; how many acres doth it contain ?
51,5X29=1135 square rods, acres, 15 rods. *A Triangle may be either right angled or oblique; in either case the teacher can easily give the scholar a right idea of the base and perpendicular, by marking it dou'r on a slate, naper, foc