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To multiply Decimals by I with any number of Ciphers, as by 10, or 100, or 1000, &c.

THIS is done by only removing the decimal point so many places farther to the right-hand, as there are ciphers in the multiplier; and subjoining ciphers if need be.

EXAMPLES.

1. The product of 51.3 and 1000 is 51300.

2. The product of 2.714 and 100 is
3. The product of 916 and 1000 is
4. The product of 21.31 and 10000 is

CONTRACTION II.

To Contract the Operation, so as to retain only as many Decimals in the Product as may be thought Necessary, when the Product would naturally contain several more Places.

SET the units' place of the multiplier under that figure of the multiplicand whose place is the same as is to be retained for the last in the product; and dispose of the rest of the figures in the inverted or contrary order to what they are usually placed in.-Then, in multiplying, reject all the figures that are more to the right-hand than each multiplying figure, and set down the products, so that their right-hand figures

may

may fall in a column straight below each other; but observing to increase the first figure of every line with what would arise from the figures omitted, in this manner, namely 1 from 5 to 14, 2 from 15 to 24, 3 from 25 to 34, &c; and the sum of all the lines will be the product as required, commonly to the nearest unit in the last figure.

EXAMPLES.

1. To multiply 27-14986 by 92.41035, so as to retain only four places of decimals in the product.

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2. Multiply 480 14936 by 2.72416, retaining only four decimals in the product.

3. Multiply 2490 3048 by 573286, retaining only five decimals in the product.

4. Multiply 325 701428 by 7218393, retaining only three decimals in the product.

DIVISION OF DECIMALS.

DIVIDE as in whole numbers; and point off in the quotient as many places for decimals, as the decimal places in the dividend exceed those in the divisor*.

*The reason of this. Rule is evident; for, since the divisor multiplied by the quotient gives the dividend, therefore the number of decimal places in the dividend, is equal to those in the divisor and quotient, taken together, by the nature of Multiplication; and consequently the quotient itself must contain as many as the dividend exceeds the divisor.

Another

Another way to know the place for the decimal point, is this: The first figure of the quotient must be made to occupy the same place, of integers or decimals, as doth that figure of the dividend which stands over the unit's figure of the first product.

When the places of the quotient are not so many as the Rule requires, the defect is to be supplied by prefixing ciphers.

When there happens to be a remainder after the division'; or when the decimal places in the divisor are more than those in the dividend; then ciphers may be annexed to the dividend, and the quotient carried on as far as required.

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178) ·48520998 (00272589 2639) 27.00000 (102.3114

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WHEN the divisor is an integer, with any number of ciphers annexed: cut off those ciphers, and remove the decimal point in the dividend as many places farther to the left as there are ciphers cut off, prefixing ciphers if need be; then proceed as before*.

* This is no more than dividing both divisor and dividend by the same number, either 10, or 100, or 1000, &c, according to the number of ciphers cut off, which, leaving them in the same proportion, does not affect the quotient. And, in the same way, the decimal point may be moved the same number of places in both the divisor and dividend, either to the right or left, whether they have ciphers or not.

EXAMPLES.

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HENCE, if the divisor be I with ciphers, as 10, 100, or 1000, &c then the quotient will be found by merely moving the decimal point in the dividend so many places farther to the left, as the divisor has ciphers; prefixing ciphers if

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WHEN there are many figures in the divisor; or when only a certain number of decimals are necessary to be retained in the quotient; then take only as many figures of the divisor as will be equal to the number of figures, both integers and decimals, to be in the quotient, and find how many times they may be contained in the first figures of the dividend, as usual.

Let each remainder be a new dividend; and for every such dividend, leave out one figure more on the right-hand side of the divisor; remembering to carry for the increase of the figures cut off, as in the 2d contraction in Multiplication.

Note. When there are not so many figures in the divisor, as are required to be in the quotient, begin the operation with all the figures, and continue it as usual till the number of figures in the divisor be equal to those remaining to be found in the quotient; after which begin the contraction.

EXAMPLES.

1. Divide 2508 92806 by 92-41035, so as to have only four decimals in the quotient, in which case the quotient will contain six figures.

Contracted.

924103,5)2508-928,06(27.1498/92-4103,5)2508-928,06 (27.1498

Contracted.

660721

13849

4608

912

Common.

66072106

13848610

46075750

91116100

79467850

5539570

80
6

2. Divide 4109.2351 by 230-409, so that the quotient may contain only four decimals. Ans. 17.8345.

3. Divide 37.10438 by 5713.96, that the quotient may contain only five decimals.

Ans. 00649.

4. Divide 913.08 by 2137.2, that the quotient may contain only three decimals.

REDUCTION OF DECIMALS.

CASE I.

To reduce a Vulgar Fraction to its equivalent Decimal.

DIVIDE the numerator by the denominator as in Division of Decimals, annexing ciphers to the numerator as far as necessary; so shall the quotient be the decimal required.

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