5. Add 11 miles, furlongs, and 30 rods together. Ans. 1m. 3 fur. 18rd. NOTE. The value of each of the fractions may be found separately, and their several values then added. 6. Add of a year, of a week, and of a day together. of a year =3 of 365 days=219 days. of a week of 7 days of a day = = 2 days 8 hours. 7. Add of a yard, of a foot, and of a mile together. Ans. yd. ft. in. 8. Add of a cut., 42 of a lb. 13oz. and of a cut. 6lb. together. Ans. 1cwt. 1qr. 27lb. 13oz. Q. How do you add fractions of different denominations? What is the second method? SUBTRACTION OF VULGAR FRACTIONS. § 107. It has been shown (see § 102), that before fractions can be added together, they must be reduced to the same unit and to a common denominator. The same reductions must be made before subtraction. SUBTRACTION of Vulgar Fractions teaches how to take a less fraction from a greater. Q. Can one-third of a shilling be subtracted from one-third of a £ without reduction? Can one-fourth of a shilling be subtracted from one-fifth of a shilling? What reductions are necessary before subtraction? What is subtraction? CASE I. § 108. When the fractions are of the same denomination and have a common denominator. RULE. Subtract the less numerator from the greater and place the difference over the common denominator. § 109. When the fractions are of the same denomination, but have different denominators. RULE. Reduce mixed numbers to improper fractions, compound fractions to simple ones, and all the fractions to a common denominator: then subtract them as in Case I. EXAMPLES. 1. What is the difference between and ? Here, ———2—3=1 answer. 6 Q. How do you subtract fractions which have the same unit but different denominators ? What is the difference between one-half and one-third? 2. What is the difference between 121 of 1 and 2 ? Ans. 2. 3. What is the difference between 2 of a £, and of a £? 4. From of 6, take 19 of 1. 5. From of of 7, take 3 of 5. 6. From 371}, take 35 of 1. CASE III. 15 Ans. £ S. Ans. 19 68 Ans. Ans. 365. § 110. When the fractions are of different denominations. RULE. Reduce the fractions to the same denomination: then reduce them to a common denominator, after which subtract as in Case I. EXAMPLES. 1. What is the difference between of a £, and of a shilling? Then, of a shilling=} of = of a £. 2 38-3-28 of a £=9s 8d. 60 Q. How do you subtract fractions which are of different denomi nations? 2. What is the difference between of a day and of a second? Ans. 3. What is the difference between 6 an inch? 4. From 13 of a lb. troy weight, take Ans. of 11hr. 59m. 59 sec. of an ounce. 5. What is the difference between of a hogshead, Ans. 16gal. 2qt. 1pt. 37gi. 6. From of a £ take of a shilling? Ans. s. d. and of a quart? 19 7. From oz. take Zpwt. 8. From 4 cwt. take 49 lb. Ans. 11pwt. 3gr. Ans. 4cwt. 1gr. 15lb. 1oz. 93dr. MULTIPLICATION OF FRACTIONS. § 111. John gave of a cent for an apple. How much must he give for 2 apples? For 3 apples? For 4? For 5? For 6? For 7? For 8? For 9? Charles gave of a cent for a peach? How much must he give for 2 peaches? For 3? For 4? For 5? For 6? EXAMPLES. 1. Multiply the fraction by 4. When it is required to multiply a fraction by a whole number, it is required to increase the fraction as many times as there are units in the multiplier, which may be done by multiplying the numerator (see § 80), or by dividing the denominator (see § 83). CASE I. 112. To multiply a fraction by a whole number. RULE. Multiply the numerator, or divide the denominator by the whole number. Q. How do you multiply a fraction by a whole number? § 113. NOTE. When we multiply by a fraction it is required to repeat the multiplicand as many times as there are units in the fraction. For example, to multiply 8 by 3 is to repeat 8, 3 times; that is, to take of 8, which is 6. Hence, when the multiplier is less than 1 we do not take the whole of the multiplicand, but only such a part of it as the fraction is of unity. For example, if the multiplier be one-half of unity, the product will be half the multiplicand: if the multiplier be of unity, the product will be one-third of the multiplicand. Hence, to multiply by a proper fraction does not imply increase, as in the multiplication of whole numbers. Q. What is required when we multiply by a fraction? What is the product of 8 multiplied by one-half? By one-fourth? By oneeighth? By three-halves? By six-halves? What is the product of 9 multiplied by one-half? By one-third? By one-sixth? By one-ninth? When the multiplier is less than 1, how much of the multiplicand is taken? Does the multiplication by a proper fraction imply increase? CASE II. § 114. To multiply one fraction by another. 1. Multiply by 5. EXAMPLES. In this example is to be taken times. That is, is first to be multiplied by 5 and the OPERATION. product divided by 7, a result which is obtained by multiplying the numerators and denominators together. Hence, we have the following RULE. Reduce all the mixed numbers to improper fractions, and all compound fractions to simple ones: then multiply the numerators together for a numerator, and the denominators together for a denominator. Q. What is the product of one-sixth by one-seventh? Of threefourths by one-half? Of six-ninths by three-fifths? Give the general rule for the multiplication of fractions. 2. Multiply of by 81. We first reduce the compound fraction to the simple one, and then the mixed number to the equivalent fraction 25; after which, we multiply the OPERATION. 1 of 3=2, 75 Hence, 25136=45· numerators and denominators together. 3. Multiply 51 by 1. Ans. 25 42' Ans. 1=1. by of 32. Ans. 23. Ans. 1431 8. Required the product of 3 of 9. Required the product of 32 by 411. 10. Required the product of 5, 3, 2 of 3 and 41. Ans. 11. Required the product of 4, of and 18. Ans. 9140 12. Required the product of 14, 5, 1 of 9 and 63. Ans. § 115. NOTE. In multiplying by a mixed number, we may first multiply by the integer, then multiply by the fraction, and then add the two products together. This is the best method when the numerator of the fraction is 1 |