1. Fractions XIV Multiplication of Fractions

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We can think of multiplying fractions as finding a fraction of another fraction.
How much is of ?
Make another with 3/4 x 2/3
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3. Real Life Example of Multiplication of Fractions
Andrea and Allison are partners in a relay race. Each girl will run half the total distance. On race day, Andrea stops for water after running of her half of the race.
What portion of the race had Andrea run when she stopped for water?
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The Brownie Problem
Nadine is baking brownies. In her family, some people like their brownies frosted without walnuts, others like them frosted with walnuts, and some just like them plain.
So Nadine frosts 3/4 of her batch of brownies and puts walnuts on 2/3 of the frosted part.
How much of her batch of brownies has both frosting and walnuts?
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Wedding Cake
Your family eats 1/8 of 1/2 of a left over wedding cake.
1/8 of 1/2 or 1/8 x 1/2
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Reading a Novel
Jose had already read 1/2 of his novel. Today he read 1/12 of the 1/2 left. How much of the book has he read?
1/12 of 1/2 or 1/12 x 1/2
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8. Multiplying Fractions Conceptual Understanding
When you multiply two fractions that are between 0 and 1 the product is smaller than both fractions.
½ x ¾ = 3/8
Look at the diagram on the
next slide to understand why.
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9. Multiplying Fractions Conceptual Understanding
½ x ¾ = 3/8
1/8
1/8
1/8
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10. How to Find a Fraction of a Fraction
The first thing to remember is “of” means multiply in mathematics. of x =
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11. How to Find a Fraction of a Fraction
Step 1 - When you see a fraction problem you know when you read “of” in the problem you multiply. 1 4 x of 2 9
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12. How to Find a Fraction of a Fraction
Step 2 – Multiply your numerators straight across. 1
x 4 4 = 2 9
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13. How to Find a Fraction of a Fraction
Step 3 – Then multiply your denominators straight across. 1
x 4 4 = 2 9 18
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14. How to Find the Fraction of a Fraction
Step 4 – Simplify your answer. In this case we simplify. 1
x 4 4 2 2 ÷ = = 2 9 18 2 9 ÷
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Multiply and Simplify 1 9 9 3 3 of ÷ x = = 6 5 30 3 10 ÷
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Multiply and Simplify 8 3 24 12 2 of x ÷ = = 9 4 36 12 3 ÷
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Multiply and Simplify 4 7 4 28 of x = 6) 28 2 3 6 24 4 2 2 ÷ 4 4 = 4 6 2 3 ÷
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Multiply and Simplify 3 3 9 27 3 8 of x = 8) 4 2 8 27 24 3
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Multiply and Simplify 2 7 8 56 9 6 of x = 6) 3 2 6 56 54 2 2 1 ÷ 9 = 9 2 6 ÷ 2 3
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Multiply and Simplify
Super job! 4 4 3 12 1 8 of x = 8) 2 4 8 12 8 4 4 1 ÷ = 1 1 4 8 4 2 ÷
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21. Multiplying Mixed Numbers In Real Life
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22. Multiplying Mixed Numbers
Try a few on your own. Remember to change your mixed numbers into improper fractions first.
Copyright © 2000 by Monica Yuskaitis