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Fractions

Fractions. Adding & Subtracting Fractions. Adding & Subtracting. Adding Fraction Strips. Line up corners on the left Find a common denominator. Arrow at the back bottom. ¼ + ½ = ¾. Subtracting Fraction Strips. Line up shapes on the right. Find a common denominator.

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Fractions

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  1. Fractions Adding & Subtracting Fractions

  2. Adding & Subtracting Adding Fraction Strips • Line up corners on the left • Find a common denominator. • Arrow at the back bottom. ¼ + ½ = ¾ Subtracting Fraction Strips • Line up shapes on the right. • Find a common denominator. • Arrow at the front bottom. ½ - 1/3 = 1/6

  3. Adding Fractions To add fractions with the same denominator, add the numerators. ¼ + ¼ = 2/4 or ½ Activity Two equal-sized pans of lasagna were used for dinner at a camp. The lasagna in one pan was cut into quarters. There was ¼ left. The lasagna in the other pan was cut into eighths. There were 3/8 left. How much lasagna was left? • Is the amount left closest to ½ a pan, 1 whole pan, or 0? • If the pan with ¼ left had been cut into eighths, how much lasagna would be left in that pan? • What is the total amount left in the 2 pans?

  4. Adding Fractions To add fractions with different denominators, write equivalent fractions with the lowest common denominator. 2/3 + 4/5 = 10/15 + 12/15 = 10 + 12 15 = 22 or 7 15 15 2/3 ½ 4/5 1 ½ + 1 = 1 ½ 1 EST

  5. Adding Fractions 2 ¾ + 3 2/3 = 2 9/12 + 3 8/12 = 5 + 9/12 + 8/12 = 5 17/12 = 6 5/12 • ¾ 3 3 2/3 4 • 3 + 4 = 7 EST

  6. Subtracting Fractions • To subtract fractions with different denominators, write equivalent fractions with the lowest common denominator. What is the LCD of 4/5 and ½ ? 4/5 = 8/10 ½ = 5/10 x 2 x 5 4/5 – ½ = 8/10 – 5/10 = 8 – 5 / 10 = 3/10

  7. Subtracting Fractions • What is the LCD of ½ and 2/3? 3 ½ - 1 2/3 = 3 3/6 - 1 4/6 ---- 3<4, so rewrite the first mixed number. = 2 9/6 - 1 4/6 --- Subtract whole numbers, then fractions. = 1 5/6 Notice that 3 3/6 and 2 9/6 are the same as 21/6, but in order to subtract you need to have the numerator on the left greater than the numerator on the right.

  8. Multiplying Fractions Multiply • ¾ x 2/5 b) 1 2/3 x 1 1/5 Solution • ¾ x 2/5 ------Multiply the numerators. Multiply the denominators. = 6/20 --------Write the answer in lowest terms. = 3/10 • Write the mixed numbers as improper fractions, then multiply. 1 2/3 x 1 1/5 = 5/3 x 6/5 = 30/15 = 2/1 or 2

  9. Multiplying Fractions • Two numbers whose product is 1 are RECIPROCALS. Since ¾ x 4/3 is 12/12 or 1 THEN: ¾ and 4/3 are known as reciprocals. Examples: Find the reciprocals a) 2/3 b)6 c) 2 ½

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