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Understanding Decimal Numbers. Reading Decimals. Say what you see before the decimal Say “and” for the decimal Say what you see after the decimal Say the place value of the final digit To write in words, you write what you say. five hundred eighty and. 5 8 0 . 3 2 4
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Understanding Decimal Numbers
Reading Decimals • Say what you see before the decimal • Say “and” for the decimal • Say what you see after the decimal • Say the place value of the final digit • To write in words, you write what you say
five hundred eightyand 5 8 0.3 2 4 three hundred twenty-four thousandths
Hundred thousandths Ten thousands ten thousandths hundreds 20 759 . 16384 tens tenths thousandths ones thousands hundredths
1 . 46 One and forty-six hundredths
67 . 4018 sixty seven and four thousand eighteen ten thousandths
12 304 . 002 Twelve thousand three hundred four and two thousandths
three and forty seven tenths Three and forty seven thousandths 3 . 47 three and forty seven hundredths Three and forty seven hundred
seventeen and eighty-two tenths seventeen and eighty-two hundredths 17 . 082 seventeen thousand eighty two seventeen and eighty-two thousandths
Zero and three thousand two three thousand two ten thousandths 0 . 3002 three thousand two three thousand two thousandths
Sixty four hundredths twenty one Six hundred forty thousand twenty one millionths 0. 640021 Six hundred forty thousand twenty one thousandths Sixty-four thousand twenty one
Modelling Decimal Numbers
1 . 4 One and four tenths
One and four tenths
Represents one whole bar Represents one tenth of a bar (meaning you need ten to make a bar) Represents one hundredth of a bar (meaning you need one hundred to make a bar) Represents one thousandth of a bar (meaning you need one thousand to make a bar)
1.07 One and seven hundredths
0.53 Fifty-three hundredths
Fifty-three hundredths or 0.53
1.245 One and two hundred forty-five thousandths
0.006 Six thousandths
1.013 One and thirteen thousandths
Comparing Decimal Numbers
Which is the larger value?0.129 or 0.31 Prove your choice!
0.129 0.129 is less than 0.31, so 0.31 is the largest value 0.31
Which is the larger value?0.2 or 0.05 Prove your choice!
0.2 0.2 is greater than 0.05 0.05
Understanding Decimal Values 45.0076 45.076 673.09 673.1 1098.44 1098.4
1. Understanding Decimal Values 67.76 67.7600 0.515 0.551 15.099 15.98
Making Connections
nine out of ten nine tenths 0.9 9 10
four tenths four out of ten 0.4 4 10
7 • 10 two wholes and seven out of ten 2.7 two and seven tenths
Thirty-two out of one hundred 0.32 thirty-two hundredths 32 100
eighty out of one hundred 0.80 eighty hundredths 80 100
six out of one hundred 0.06 six hundredths 6 100
Three and two hundredths 3.02 • 2 • 100 Three wholes and two parts out of a hundred
2 14 100 Two and fourteen hundredths 2.14 Two wholes and fourteen out of one hundred
Decimals in Expanded Form
Decimals in Expanded Form • Writing decimals in expanded form is an extension of whole numbers in expanded form. • To do this you represent each individual place value EXAMPLE 4.305 is • 4 + 0.3 + 0.005 • 4 x 1 + 3 x 0.1 + 5 x 0.001 • 4 x 100 + 3 x 10-1 + 5 x 10-3
Decimals in Expanded Form • 34.308 • 30 + 4 + 0.3 + 0.008 • 3 x 10 + 4 x 1 + 3 x 0.1 + 8 x 0.001 • 3 x 101 + 4 x 100 + 3 x 10-1 + 8 x 10 -3 • 5.28 • 5 + 0.2 + 0.08 • 5 x 1 + 2 x 0.1 + 8 x .01 • 5 x 100 + 2 x 10-1 + 8 x 10-2
Decimals in Expanded Form 3.49 90.35 • 3 + 0.4 + 0.09 = • 9 x 101 + 3 x 10-1 + 5 x 10-2 = • 40 + 0.8 + 0.003 = • 0.7 + 0.03 + 0.0002 = • 0.06 + 0.4 + 3 + 20 + 0.001 = • 800 + 3 + 60 000 + 0.02 + 0.007 = 40.803 0.7302 23.461 60 803.o27
Decimals in Expanded Form 4000.53 • 4 x 1000 + 5 x 0.1 + 3 x 0.01 = • 7 x 100 + 2 x 0.1 + 5 x 1 + 8 x 0.001 = • 4 x 0.0001 + 3 x 0.1 + 2 x 0.01 = • 0.006 + 0.01 + 700 + 20 + 0.0004 = • 3 x 1 + 4 x 0.01 = • 8 x 100 + 5 x 10-2 + 3 x 10-3 = 705.208 0.3204 720.0164 3.04 8.053