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# FraCtiOnS muLtiPliCatiOns

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### FraCtiOnS muLtiPliCatiOns

1. 1. FractionMultiplication And Cancelation
2. 2. Fraction Multiplication• Here are some fraction multiplication problems 4 1 4• Can you tell how to × = multiply fraction from 5 7 35 these examples? 2 5 10 2 5 10 × = × = 3 1 3 3 7 21 3 5 15 1 1 1 × = × = 4 12 48 3 3 9 6 4 24 × = 5 10 50
3. 3. Multiplication• Multiply numerator by numerator• And denominator by denominator 2 5 10 × = 3 1 3 N1 N 2 N1 × N 2 × = D1 D 2 D1 × D 2
4. 4. Try some.• Multiply the following: 1 5 5 5 × = × = 3 8 8 8 2 4 4 2 × = × = 3 5 9 3
5. 5. Answers• Multiply the following:1 5 5 5 5 25 × = × =3 8 24 8 8 64 2 4 8 4 2 8 × = × = 3 5 15 9 3 27
6. 6. Mixed Numbers• Because of the order of operations,• Mixed numbers cannot be multiplied as is• Change mixed numbers to improper fractions, then multiply. 2 5 3 ×1 = 5 8 17 13 17 13 221 × = × = 5 8 5 8 40 221 ÷ 40 = 5 with a remainder of 21 21 5 40
7. 7. Try some• Change any whole or mixed numbers to improper.• Multiply straight across.• Simplify answers 2 1 1 ×7 = ×8 = 5 5
8. 8. Answers• Change any whole or mixed numbers to improper.• Multiply straight across.• Simplify answers 2 7 7 49 4 1 ×7 = × = =9 5 5 1 5 5 1 1 8 8 3 ×8 = × = =1 5 5 1 5 5
9. 9. Cancelling Reduce before you multiply
10. 10. Canceling• Reducing before mutiplying is called canceling. 25 12 300 × = 32 35 1120• ICK! Instead think the following in your head. 25 12 25 × 12 5 × 5 × 4 × 3 × = = 32 35 32 × 35 8 × 4 × 7 × 5 5 × 5 × 4 × 3 5 × 3 15 = = 8 × 4 × 7 × 5 8 × 7 56
11. 11. Canceling on paper• Rules: One factor from any numerator cancels 16 9 15 with like factor from the × × denominator. 21 20 12 11 4 3 1 313 1 444 3 16 × 99 × 1515 = 3 16 × 99 × 15 16 16 16 9 15 15 3 3 21 7 × 4 20 ××12 ×× × 7 21 21 21 21 20 12 20 12 3 120 444 20 12 3 3 1 31 4 1 1
12. 12. Try one• Say “--- goes into ____ this many times.”• As you cross each number out and write what is left after canceling above the number. 5 1 × 3 10
13. 13. Answer• Say “--- goes into ____ this many times.”• As you cross each number out and write what is left after canceling above the number. 1 5 1 5 × = 3 10 2 6
14. 14. Try one more• Make whole and mixed numbers improper• Cancel if you can• Multiply Numerators and denominators straight across.• Simplify 10 1 14 ×4 × ×4 21 2 15
15. 15. Answer• Make whole and mixed numbers improper• Cancel if you can• Multiply Numerators and denominators straight across.• Simplify 10 1 14 ×4 × ×4 21 2 15 10 9 14 4 × × × =8 21 2 15 1