Note When we multiply 1 2 by 3 3 , we do not change the value of the fraction because 3 3 1. Multiplying 1 2 by 3 3 gives us the equivalent fraction 3 6 . To add and subtract unlike fractions, we must know how to write a given fraction as an equivalent fraction with a different denominator. Let’s practice that now. Write 3 4 as an equivalent fraction with a denominator of 20. Solution We must fi nd a fraction that is equivalent to 3 4 so that 3 4 ? 20 . Ask yourself, “By what number do I multiply 4 to get 20?” That number is 5: 4 5 20. Multiply the numerator and denominator of 3 4 by 5: 3 4 5 5 15 20 aRemember, 5 5 1, so multiplying 3 4 by 5 5 does not change the value of the fraction; it gives us an equivalent fraction.b YOU TRY 1 Rewrite 7 8 as an equivalent fraction with a denominator of 32. Procedure Writing a Fraction with a Different Denominator Step 1: Ask yourself, “By what number do I multiply the original denominator to get the new denominator?” Step 2: Multiply the numerator and denominator of the original fraction by that number to get the equivalent fraction. Write each fraction with the indicated denominator. a) 4 7 ? 56 b) 1 12 ? 72 Solution a) Step 1: Ask yourself, “By what number do I multiply 7 to get 56?” That number is 8. Step 2: Multiply the numerator and denominator of 4 7 by 8: 4 7 8 8 32 56 Therefore, 4 7 32 56 . EXAMPLE 1 EXAMPLE 2 236 CHAPTER 4 Adding and Subtracting Fractions www.mhhe.com/messersmith
messersmith_power_basic_college_1e_ch4_7_10
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