Εικόνες σελίδας
PDF
Ηλεκτρ. έκδοση

Fractions.

II. THE DIVISION ASPECT.

The numerator of a fraction is a dividend; the denominator, a divisor, and the fraction itself, a quotient : thus, in the fraction, the dividend is 5; the divisor, 8, and the quotient, .

NOTE.-In the case of an improper fraction, as ļ, it may be more readily seen by the pupil that the numerator is the dividend, the denominator the divisor, and the fraction (i=2) the quotient; but the division relation is in every fraction, whether proper or improper, common or decimal, simple or complex,

III. THE RATIO ASPECT.

The numerator of a fraction is an antecedent; the denominator, a consequent, and the fraction itself, a ratio: thus, in the fraction 16, 7 is the antecedent, 10 the consequent, and to the ratio.

Note 1.—This relation may be more readily seen by the pupil in the case of an improper fraction. In the fraction 1?, 12 is the antecedent; 4, the consequent; 42, or 3, the ratio.

NOTE 2.-Every integral number as well as every fraction is a ratio. The number 8 is the ratio of a magnitude that is 8 times some unit of measurement to a magnitude that is 1 time the same unit of measurement. 8 (units of measurement) is the antecedent; 1 (unit of measurement) is the consequent, and the pure number 8 is the ratio.

178. REDUCTION OF FRACTIONS.

1. The numerator and the denominator of a fraction are its terms.

2. A fraction is said to be in its lowest terms when its numerator and denominator are integral numbers that are prime to each other.

Fractions.

3. Reduce 16; to its lowest terms.

10);

Operation.

Explanation. 160 16

Dividing each term of 188 by 10 we have 200

20 1 tenth as many parts, which are 10 times as 16 4

large. Dividing each term of 28 by 4 we have 4);

1 fourth as many parts, which are 4 times as 20 5

large. Hence, 188 = . But 4 and 5 are prime to each other, and the fraction is in its lowest terms.

RULE. - Divide each term of the fraction by any common divisor except 1, and divide each term of the fraction thus obtained by any common divisor except 1, and so continue until the terms are prime to each other.

[blocks in formation]

(a) Find the sum of the ten results. I 4. Reduce & to higher terms to 120ths.

[blocks in formation]

* Divide each term by 123. This involves the reduction of a complex to a simple fraction; but it will lead to thoughtful work for the pupil to solve such problems in this manner.

+ Divide each term by 2.

# If the pupil has not had sufficient practice in addion of fractions to do this the finding of the sum may be omitted until the book is reviewed.

Fractions.

5

Reduce to higher terms to 160ths.
(1) 8
(2) 13

(3) 26
(5)
(6)
(7)

(8) 23
(9) 33 (10) 83
(a) Find the sum of the ten results.

5. Two or more fractions whose denominators are the same, are said to have a common denominator.

6. Two or more fractions that do not have a common denoninator may be changed to equivalent fractions having a cominon denominator.

EXAMPLE.
and may be changed to 12ths, 24ths, or 36ths.

33 용 i 23 용 을

24

24

36

36

7. Two or more fractions that do not have a common denominator may be changed to equivalent fractions having their least common denominator. The 1. c. d. of two or more fractions is the 1. c. m. of the given denominators.

EXAMPLE Change 1, 2, and 37 to equivalent fractions having their least common denominator.

OPERATION.

(1) The 1. c. m. of 30, 40, and 60 is 120.

11 X 4 44 (2) 120 30 4

30 x 4 120

9 X 3 27 (3) 120 – 40 3

40 x 3 120

37 x 2 74
(4) 120 + 60 2

60 X 2 120
38 = 120, 1 = $ 37 = 12%

Fractions.

Reduce to equivalent fractions having their 1. c. d. (1) 15 and 26

(6) 15, , and (2) if and 13

(7), ), and go (3) }; and 17

(8) 37, Ķ, and (4) 3 and out

(9) 8, 16, and
(5) 4 and 7

(10) 1, 2, and
(a) Find the sum of the twenty-five fractions. *

179. To add common fractions.

RULE.— Reduce the fractions if necessary to equivalent fractions having a common denominator, add their num tors, and write their sum over the common denominator.

EXAMPLE.

Add 1), f), and 3.
(1) The 1. c. m. of 45, 30, and 60, is 180.
(2) 13 = 180. 17 = 186. 68 = 18%.
(3) 1458 + 18% + 188 = 186.

NOTE.-If the work that precedes this article has been well done, no explanation of the foregoing will be necessary. Pupils have already learned (presumably before using this book) (1) that fractions may be reduced to higher terms, (2) that two or more fractions whose denominators are not alike may be reduced to higher terms with like denominators, (3) that a common denominator of two or more fractions with unlike denominators, is a common multiple of the given denominators, and (4) that in reducing a fraction to higher terms the numerator and denominator must be multiplied by the same number. The simple problem of adding 44 180ths, 102 180tiis, and 159 180ths, is not unlike the problem of adding 44 apples, 102 apples, and 159 apples.

(For a continuation of this work, see page 91.)

* This work may be omitted until the subject of fractions is reviewed.

Algebraic Fractions.

a

X

6 180. The expressions

b' 4 d

are algebraic fractions.

The above expressions are read, a divided by b; x divided by 4; S divided by cd.

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]
[ocr errors]

a

3.

[blocks in formation]

a

Let a = 2, 6 3, c = 5, and d

7, and verify. Observe that to reduce a fraction to its lowest terms we have only to strike out the factors that are common to its numerator and denominator.

a b 4.

What factors are common to both numerator and ac denominator ? Reduce and verify.

r 13 5.

What factors are common to both numerator and ya maeneo denominator ? Reduce and verify.

[merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]
« ΠροηγούμενηΣυνέχεια »