Report

Adding & Subtracting Fractions Teacher Notes: • Use this presentation to teach the steps for adding and subtracting fractions with unlike denominators. • It is assumed that students have a thorough understanding of the process for making equivalent fractions. • CLICK HERE to view a demonstration with opportunities for students to practice making equivalent fractions. We need a common denominator to add these fractions. We need a common denominator to add these fractions. 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 7, 14, 21, 28, 35… 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 7, 14, 21, 28, 35… The first number IN COMMON that appears on both lists becomes the common denominator x7 7 X7 x2 6 7 + 6 = 13 x2 13 We need a common denominator to add these fractions. 7, 14, 21, 28, 35, 42, 49, 56, 63 5, 10, 15, 20, 25, 30, 35, 40, 45 x5 15 X5 x7 7 x7 15 + 7 = 22 22 We need a common denominator to add these fractions. 7, 14, 21, 28, 35, 42, 49, 56, 63 8, 16, 24, 32, 40, 48, 56, 64, 72 x8 32 x8 x7 21 32 + 21 = 53 x7 53 We need a common denominator to add these fractions. 3, 6, 9, 12, 15, 18, 21, 24, 27 5, 10, 15, 20, 25, 30, 35, 40, 45 x3 9 X3 x5 9 + 10 = 19 10 x5 19 We need a common denominator to add these fractions. 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 11, 22, 33, 44, 55, 66, 77… x3 15 X3 x 11 22 15 + 22 = 37 x 11 37 We need a common denominator to add these fractions. 3, 6, 9, 12, 15, 18, 21, 24, 27 6, 12, 18, 24,… x2 4 X2 x1 1 x1 5 4+1=5 We need a common denominator to add these fractions. 11, 22, 33, 44, 55, 66, 77… 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72 x6 18 X6 x 11 11 18 + 11 = 29 x 11 29 We need a common denominator to add these fractions. We need a common denominator to add these fractions. 5, 10, 15, 20, 25, 30, 35, 40, 45 9, 18, 27, 36, 45, 54, 63, 72, 81 5, 10, 15, 20, 25, 30, 35, 40, 45 9, 18, 27, 36, 45, 54, 63, 72, 81 The first number IN COMMON that appears on both lists becomes the common denominator x9 36 x9 x5 35 x5 71 36 + 35 = 71 We need a common denominator to add these fractions. 12, 24, 36, 48, 60, 72, 84, 96 8, 16, 24, 32, 40, 48, 56, 64, 72, 79, 80, 88, 96 x2 10 x2 x3 9 10 + 9 = 19 x3 19 We need a common denominator to subtract a fraction from another. 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 11, 22, 33, 44, 55, 66, 77… x5 15 x5 x 11 11 15 - 11 = 4 x 11 4 We need a common denominator to subtract one fraction from another. 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 … 10, 20, 30… x5 5 x5 x1 3 5–3= 2 x1 2 Try These A D B E C F Answers On Next Slide • Each click on the next slide reveals an answer. • Check your papers. • If you discover an incorrect answer, be able to explain your mistake. Try These 17 27 D 10 9 B 13 12 E 41 28 C 19 20 F 26 21 A