Reducing Numeric Fractions

Turn Mystery into Mastery

?875

140

C2006 – DW Vandewater

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Suggestion:

Work with scratch paper and pencil as you go through this presentation.

Powerpoint 2007: Click on SLIDESHOW, then click on FROM BEGINNING

Powerpoint 2003: Click on BROWSE, then click on FULL SCREEN

25

4

)5)(5(

)2)(2(

)7)(5)(5)(5(

)7)(5)(2)(2(

875

140

What if we could look at a simplified form of both numbers?

1. Figure out the prime factors of both.2. Do any factors cancel out? Cancel them.3. Write the remaining factors.4. Multiply the tops.5. Multiply the bottoms. That’s the simplest form of the fraction!

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What is the Key Skill?

Prime Factorization! (A big name for a simple process …)

Finding out how to write a number as the product of it’s prime factors.

Examples:

6 = 2∙370 = 2∙5∙724 = 2∙2∙2∙313=13 because 13 is prime (no

other factors)Click to Advance

Practice:Let’s Reduce a Fraction

Here’s the problem ->◦ Find the prime factors of 48◦ Find the prime factors of 144◦ Rewrite the fraction w/ primes◦ Cancel matching factors

◦ Rewrite the fraction

◦ Multiply top & bottom, if necessary

That is the simplest form

144

4832/\62\2/12\4/22\8/4

332222

32222

3

1

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3232/\6

/\6\6/32\2/72\4/14

Practice:Let’s Reduce a Bigger Fraction

Here’s the problem ->◦ Find the prime factors of

1848◦ Find the prime factors of

990◦ Rewrite the fraction◦ Cancel matching factors

◦ Rewrite the fraction

◦ Multiply top & bottomThat is the simplest form

990

18481173222

773222231222

462229242

1848

115332

55332

16532

4952

990

115332

1173222

53

722

15

28

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More PracticeSee if you can find the simplest forms.

Do the work on paper and click to see the answer

5

18

5

332

752

73322

70

252

551

115

133

131153

39

2145

66

13

1132

13

11732

137

462

91

primeboth101

59

101

59

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Thank YouFor Learning about

◦Prime Factorization◦Reducing Numeric fractions