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Multiplying and Dividing Multiplying and Dividing Decimals By Powers of 10.Decimals By Powers of 10.Multiplying and Dividing Multiplying and Dividing

Decimals By Powers of 10.Decimals By Powers of 10.

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Multiplying by Powers of 10Multiplying by Powers of 10

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Warm-upWarm-up 5.3 x 9 =47.75.3 x 9 =47.7 7.2 ÷ 0.4=18 7.2 ÷ 0.4=18 7 x 8.39 =58.737 x 8.39 =58.73 0.006 ÷ 0.3 =0.020.006 ÷ 0.3 =0.02 9.7 x 0.8 =7.769.7 x 0.8 =7.76 1.8 x 1.23 =2.2141.8 x 1.23 =2.214 2.9 x 0.06= 0.1742.9 x 0.06= 0.174 90.3 ÷ 6=15.0590.3 ÷ 6=15.05 246.5 ÷ .2465=1000246.5 ÷ .2465=1000

Practice it

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Multiplying by 10Multiplying by 10

Multiplying by 10 moves the Multiplying by 10 moves the decimal point one place to the decimal point one place to the right.right.

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ExamplesExamples

10 10 x 0.389 = 03.89x 0.389 = 03.89 10 10 x 3.89 = 38.9x 3.89 = 38.9 10 10 x 38.9 = 389x 38.9 = 389

0 . 3 893. 8 9

38. 9

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ProblemsProblems 10 x 5.623 =56.23

0.1 x 10 =1

0.001 x 10 =0.01

0.01 x 10 =0.1

7.8 x 10 =78

28.256 x 10 =282.56

19.52 x 10=195.2

Look for a pattern.

Watch the decimal points.

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Multiplying by 100Multiplying by 100

Multiplying by 100 moves Multiplying by 100 moves the decimal point the decimal point two places to the right.places to the right.

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ExamplesExamples

100 x 0.795 = 79.5100 x 0.795 = 79.5 100 x 7.95 = 795100 x 7.95 = 795 100 x 79.5 = 7950100 x 79.5 = 7950

0. 79 57. 95

79.50 Extra zero

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LET’S PRACTICELET’S PRACTICE O.2 X 100 =20

0.02 X 100 =2

0.002 X 100 =0.2

7.8 X 100 =780

19.52 X 100 =1952

28.256 X 100 =2825.6

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MULTIPLYING BY MULTIPLYING BY 10001000

MULTIPLYING BY 1000 MOVES MULTIPLYING BY 1000 MOVES THE DECIMAL POINT THE DECIMAL POINT THREE THREE PLACES TO THE RIGHT.PLACES TO THE RIGHT.

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EXAMPLES:EXAMPLES:

1000 X 2.359 = 23591000 X 2.359 = 2359

1000 X 23.59 = 235901000 X 23.59 = 23590

2. 3 5 9

23. 590 EXTRA ZERO

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PROBLEMSPROBLEMS

28.256 X 1000 =28,256 19.52 X 1000 =19520

7.8 X 1000 =7800

0.3 X 1000 =300

0.03 X 1000 =30

0.003 X 1000=3

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BreakBreak

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DIVIDING BY POWERS OF DIVIDING BY POWERS OF 1010

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DIVISION BY 10, 100, 1000DIVISION BY 10, 100, 1000

WHEN DIVIDING BYWHEN DIVIDING BY THE DECIMAL POINT THE DECIMAL POINT MOVES TO THE LEFT MOVES TO THE LEFT BYBY

1010 1 DECIMAL PLACE1 DECIMAL PLACE

100100 2 DECIMAL PLACES2 DECIMAL PLACES

10001000 3 DECIMAL PLACES3 DECIMAL PLACES

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EXAMPLESEXAMPLES

a)a) 321.5 ÷ 321.5 ÷ 10 10 = 32.15= 32.15

b)b) 321.5 ÷ 321.5 ÷ 100 100 = 3.215= 3.215

c)c) 321.5 ÷ 321.5 ÷ 1000 1000 = = 0.32150.3215

321.5

321.5

321.5

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ProblemsProblems 4 ÷ 10 =0.4 2.35 ÷ 100=0.02350 0.288 ÷ 100 =0.00288 357 ÷ 1000 =0.357 243 ÷ 100000

=0.00243

6.3 ÷ 10=0.63

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Just try this!!!Just try this!!!

http://www.jigzone.com/puzzles/A7055D506E99?z=10

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Mixed PracticeMixed Practice

5.3 x 100 =530 0.84 x 10 =8.4 17.42 x 1000 =17420 1.235 x 100000 =123500 0.00007 x 1000000 =70

4.35 ÷ 100=0.0435

21.5 ÷ 10 =2.15

8.79 ÷ 10000=0.000879

0.0594 ÷ 1000=0.0000594

0.27222÷10000=.000027222

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ReviewReview

Multiplying by powers of 10 shifts the decimal places to the right of the decimal in the question according to the number of zeroes in the powers of 10.

Dividing by powers of 10 moves the decimal places to the left of the decimal in the question according to the number of zeroes in the powers of 10.

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