c) Do we need a common denominator to fi nd 21 8 14 3 ? No! We do not need a common denominator to divide, or multiply, fractions. To divide fractions, multiply the fi rst fraction by the reciprocal of the second. 21 8 14 3 21 8 3 14 Change division to multiplication by the reciprocal. Divide 21 and 14 by 7. Multiply. 3 21 8 3 14 2 3 3 8 2 9 16 Ask yourself, “Is 9 16 in lowest terms?” Yes. d) What is the fi rst step for fi nding 8 9 10 3 4 5 ? Write 9 10 and 4 5 as equivalent fractions with an LCD. The LCD of 9 10 and 4 5 is 10. 9 10 already has the LCD. 4 5 2 2 8 10 8 9 10 3 4 5 8 9 10 3 8 10 Write the fractions with the LCD. 1 10 5 Subtract whole numbers, and subtract fractions. Is 5 1 10 in lowest terms? Yes. e) How do we fi nd 3 5 12 9 4 5 ? Write 5 12 and 4 5 as equivalent fractions with their least common denominator. Then, add the whole-number parts, and add the fractional parts. 3 5 12 9 4 5 3 25 60 9 48 60 Write the fractions with the LCD. 73 60 12 Add. Is 12 73 60 in simplest form? No! 73 60 is an improper fraction. Simplify 12 73 60 by regrouping. 12 73 60 12 73 60 12 1 13 60 13 13 60 So, 3 5 12 9 4 5 13 13 60 . The answer is in lowest terms. 268 CHAPTER 4 Adding and Subtracting Fractions www.mhhe.com/messersmith
messersmith_power_basic_college_1e_ch4_7_10
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