« ΠροηγούμενηΣυνέχεια »
To change Improper Fractions to Integers or to Mixed
Numbers. 204. A fractional number, the numerator of which equals or exceeds the denominator, is called an improper fraction.
205. ILLUSTRATIVE EXAMPLE III. Change and as far as possible to integers.
Explanation. — (1.) Since 12 twelfths make a (1.) 12) 60 unit, in 60 twelfths there are as many units as
there are 12's in 60, which is 5. Ans. 5.
(2.) In 17 there are as many units as there are
12's in 47, which is 3 and 4t. Ans. 3 14. (2.) 12) 47
206. The number 3 11 consists of an Ans. 31}
integer and a fraction. A number consisting of an integer and a fraction is a mixed number.
207. Oral Exercises. a. Change to integral numbers: $ ; ; ; ; 40; $; 4; 3; 4; 3; 4; 5; 7; ft; 4; 4; 4,0; $8.
b. Change to mixed numbers: ; ; 12; 12; 12; *; ; 32; 12; 1; ;46; 11; 18; 3; 4; 4.
c. Change to integers or to mixed numbers : %; ; ; 38 ; 5,5; 4; 54 ; it; 17; 198 ; ; 62.
208. From previous illustrations we may derive the following
Rule. To change an improper fraction to an integer or a mixed number : Divide the numerator by the denominator.
209. Examples for the Slate. Change to integers or to mixed numbers: (13.) 14 (15.) 4 (17.) 1964 (19.) 4,7 days. (14.) 1938 (16.) 6722 (18.) 2:9 (20.) 934 years.
To change an Integer or a Mixed Number to an Improper
210. ILLUSTRATIVE EXAMPLE IV. Change 231 to fourths.
Explanation. Since in 1 there are 4 fourths, in 234 = Ans. 23 there are 23 times 4 fourths, or 92 fourths, 4 which, with 1 fourth added, are 93 fourths.
211. Oral Exercises.
à. Change to improper fractions : 2}; 38; 23; 5; 24; 3%; 6}; 5; 5}; 73; 7}; 8; 8; 9}; 9; 103.
b. Change to improper fractions: 28; 23 ; 31 ; 34; 4); 49; 58; 94 ; 64; 7; 8; 94 ; 44; 43 ; 8}; 77.
c. Change 5 to ninths; 11 to fifths ; 14 to thirds ; twelfths; 15 to fourths; 1 to sevenths.
d. Among how many persons must 7 melons be divided that each may receive of a melon ? ? ? ?
e. How many persons will 5} cords of wood supply if each person receives } of a cord ? 4 of a cord ? ☆ of a cord ?
212. From previous illustrations may be derived the following
Rule. To change an integer or a mixed number to an improper fraction: Multiply the integer by the denominator of the fraction, and to the product add the numerator; the result will be the numerator of the required fraction.
213. Examples for the Slate. Change the following to improper fractions : (21.) 694 (24.) 7641 (27.) Change 48 to ninths. (22.) 2721. (25.) 10745
(25.) 1074. (28.) Change 567 to tenths. (23.) 10925. (26.) 667. (29.) Change 93 to forty-thirds.
For other examples in reduction of fractions, see page 123.
ADDITION OF FRACTIONS.
To add Fractions having a Common Denominator.
214. ILLUSTRATIVE EXAMPLE I. Add af of an apple, šof an apple, and } of an apple. Ans. f of an apple.
These fractions are like parts (eighths) of the same or similar units (apples). Such fractions are like fractions.
215. Like fractions have the same denominator, which, because it belongs to several fractions, is called a common denominator.
216. Oral Exercises.
a. Add 1 ts, and is
e. Add to do, and 44.
How do you add fractions which have a common denominator ?
To add Fractions not having a Common Denominator. 217. ILLUSTRATIVE EXAMPLE. Add &, f, and 15.
Explanation. – To be added, these 2 x 3 x 3 x 5 = 90 1. c. denom.
fractions must be changed to like frac
tions, or to fractions having a common 各
denominator. (Art. 215.) The new
denominator must be some multiple of Yo = 757 = %
the given denominators. A convenient Ans. 19 = 187. multiple is their least common multiple,
which is 90. (Art. 182.) To change & to 90ths, the denominator 6 must be multiplied by 3x5, or 15; hence the numerator 5 must be multiplied by 15. (Art. 199.) Thus, á is found to equal 7%.
In a similar way $ will be found to equal f, and to equal . Adding these fractions, we have 37, or 157, for the sum.
218. Oral Exercises.
a. Add d, 4, and .
Ans. 1s = b. Add , , and .
Ans. 7* = 23.
c. Add }, &, and 3.
NOTE. When the denominators are prime to each other, the new denomi. nator will be the product of all the denominators, and the new numerators will be found by multiplying each numerator by the product of all the denominators except its own.
g. Add } and }; } and }; 1 and }; } and }; it and }; and ; } and 10; } and }. h. Add ; and }; and ; and ; and }; } and $. i. Add }, }, and ? ; }, }, and }; }, 4, and }; TU, $, and }.
j. If you should spend ļ of your time in school, 4 in practising music, and ß in sewing and studying, what time would you spend in all ?
k. Owning f of a paper-mill, I bought the shares of two other persons who owned by and respectively. What part of the mill did I then own ?
219. From the above examples may be derived the following
Rule. To change fractions to equivalent fractions having the least common denominator :
1. For the common denominator, find the least common multiple of the given denominators.
2. For the new numerators, multiply the numerator of each fraction by the number by which you multiply its denominator to produce the common denominator.
NOTE. If the number to multiply the numerator by is not readily seen, it may be found by dividing the common denominator by the denominator of the given fraction.
220. From what we have now learned of the addition of fractions, we may derive the following
Rule. To add fractions :
1. If they have a common denominator, add their numerators.
2. If they have not a common denominator, change then to equivalent fractions that have a common denominator, and then add their numerators.
221. Examples for the Slate.
(30.) 4+ % + } + = ?
(35.) * +75 + }} = ?
Add the integers and fractions of the following, and similar examples, separately :
40. In my furnace there were burned 24 tons of coal in December, 23 tons in January, and 3 in February. How many tons were burned in all ? (41.) 72} +164 + 183 +234 +3715 = ?
42. A horse travelled 431 miles in one day, 524 the next, 364 the third, and 4037 the fourth. How far did he travel in all ?
43. A merchant had three barrels of sugar, the first containing 247} pounds; the second, 229 pounds; and the third, 2607 pounds. What was the weight of the whole ?
For other examples in addition of fractions, see page 123.
* What operation should first be performed on this fraction ?