CHAPTER IV. FRACTIONS. 76. A fractional unit is any one of a number of equal parts 1 1 1 1 of a unit. Thus, Ő are fractional units. 77. A fraction is a fractional unit, or a collection of 1 3 5 a fractional units. Thus, a 2' A' ñ are fractions. 78. Every fraction is composed of two parts, — the denominator and the numerator. The denominator shows into how many equal parts the unit 1 is divided ; and the numerator, how many of these parts are taken. Thus, in the fraction 9, the denominator 6 shows that 1 is divided into 6 equal parts, and the numerator a shows that a of these parts are taken. The fractional unit, in all cases, is equal to the reciprocal of the denominator. 79. An entire quantity is one which contains no fractional part. Thus, 7, 11, aRx, 4x2 – 3y, are entire quantities. An entire quantity may be regarded as a fraction whose denominator is 1. Thus, 7 = 1, ab=46. 80. A mixed quantity is a quantity containing both entire and fractional parts. Thus, 74, 84, a + b2, are mixed quantities. are 81. Let om denote any fraction, and q any quantity whatever. From the preceding definitions, denotes that is taken a times ; ' also af denotes that į is taken aq times, ever. that is, Hence Multiplying the numerator of a fraction by any quantity is equivalent to multiplying the fraction by that quantity. We see, also, that Any quantity may be multiplied by a fraction by multiplying it by the numerator, and then dividing the result by the denominator. 82. It is a principle of division that the same result will be obtained if we divide the quantity a by the product of two factors, p X q, as would be obtained by dividing it first by one of the factors, p, and then dividing that result by the other factor, q; that is, Hence Multiplying the denominator of a fraction by any quantity is equivalent to dividing the fraction by that quantity. 83. Since the operations of multiplication and division are the converse of each other, it follows, from the preceding principles, that Dividing the numerator of a fraction by any quantity is equivalent to dividing the fraction by that quantity. Dividing the denominator of a fraction by any quantity is equivalent to multiplying the fraction by that quantity. 84. Since a quantity may be multiplied and the result divided by the same quantity without altering the value, it follows that Both terms of a fraction may be multiplied by any quantity, or both divided by any quantity, without changing the value of the fraction. . TRANSFORMATION OF FRACTIONS. 85. The transformation of a quantity is the operation of changing its form without altering its value. The term “reduce” has a technical signification, and means “to transform." 86. To reduce an Entire Quantity to a Fractional Form having a Given Denominátor. Let a be the quantity, and b the given denominator. We have, evidently, a=6 Hence the rule : Multiply the quantity by the given denominator, and write the product over this given denominator. 87. To reduce a Fraction to its Lowest Terms. A fraction is in its lowest terms when the numerator and the denominator contain no common factors. It has been shown that both terms of a fraction may be divided by the same quantity without altering its value: therefore, if they have any common factors, we may strike them out. Hence the rule :— . Resolve each term of the fraction into its prime factors, then strike out all that are common to both. The same result is attained by dividing both terms of the fraction by any quantity that will divide them without a remainder, or by dividing them by their G. C. D. |