Multiplying and Dividing Decimals By Powers of 10

CONFIDENTIALCONFIDENTIAL 11

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.

CONFIDENTIALCONFIDENTIAL 22

Multiplying by Powers of 10Multiplying by Powers of 10

CONFIDENTIALCONFIDENTIAL 33

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

CONFIDENTIALCONFIDENTIAL 44

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.

CONFIDENTIALCONFIDENTIAL 55

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

CONFIDENTIALCONFIDENTIAL 66

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.

CONFIDENTIALCONFIDENTIAL 77

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.

CONFIDENTIALCONFIDENTIAL 88

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

CONFIDENTIALCONFIDENTIAL 99

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

CONFIDENTIALCONFIDENTIAL 1010

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.

CONFIDENTIALCONFIDENTIAL 1111

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

CONFIDENTIALCONFIDENTIAL 1212

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

CONFIDENTIALCONFIDENTIAL 1313

BreakBreak

CONFIDENTIALCONFIDENTIAL 1414

DIVIDING BY POWERS OF DIVIDING BY POWERS OF 1010

CONFIDENTIALCONFIDENTIAL 1515

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

CONFIDENTIALCONFIDENTIAL 1616

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

CONFIDENTIALCONFIDENTIAL 1717

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

CONFIDENTIALCONFIDENTIAL 1818

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

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

CONFIDENTIALCONFIDENTIAL 1919

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

CONFIDENTIALCONFIDENTIAL 2020

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.

CONFIDENTIALCONFIDENTIAL 2121