The decimal point helps us to keep track of where the "ones" place is. 4/17/2017 In our number system, digits can be placed to the left and right of a decimal point, to indicate numbers greater than one or less than one. 1.0 or 0.1 The decimal point helps us to keep track of where the "ones" place is. It's placed just to the right of the ones place. As we move right from the decimal point, each number place is divided by 10. 1

Parts of the number 4/17/2017 The whole number portion of a decimal number are those digits to the left of the decimal place. Example: In the number 23.65, the whole number portion is 23. In the number 0.024, the whole number portion is 0. What are the decimal portions of these numbers? 2

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Five hundred forty-eight thousandths 0.548 4/17/2017 Hint #1: Remember to read the decimal point as "and" -- notice in the last two problems what a difference that makes! Five hundred and forty-eight thousandths 500.048 Hint #2: When writing a decimal number that is less than 1, a zero is normally used in the ones place: Five hundred forty-eight thousandths 0.548 0.548 not .548 5

Expanded Form of a Decimal Number 4/17/2017 Expanded Form of a Decimal Number Expanded Form of a Decimal Number The expanded form of a decimal number is the number written as the sum of its whole number and decimal place values. Example: 3 + 0.7 + 0.06 + 0.002 = 3.762 100 + 3 + 0.06 = 103.06 6

Just a Note… BUT The number 14.504 is equal to 14.504000 4/17/2017 Just a Note… The number 14.504 is equal to 14.504000 Adding extra zeros to the right of a decimal number does not change its value BUT The number 14,505 ≠14,504,000 7

4/17/2017 Adding Decimals 8.4 + 1.22 = 8.4 + 1.22 9.62 12.924 + 3.6 = 12.924 +3.600 16.524 ALWAYS be sure to stack the numbers so the decimals stay above one another!!! 8

Subtracting Decimals 10.66 – 5.22 = 10.66 -5.22 5.44 4/17/2017 Subtracting Decimals 10.66 – 5.22 = 10.66 -5.22 5.44 18.2 - 6.008 = Add extra 0's, using the fact that 18.2 = 18.200 18.200 - 6.008 12.192 9

4/17/2017 Multiplying Decimals If not using a calculator, count the number of decimal places in all terms to be multiplied The answer should contain that many decimal places. 5.222 m x 4.11m 21.46242 m2 (5 decimal places) 10

Dividing with Decimals 4/17/2017 Dividing with Decimals 11

Dividing Decimals Dividend ÷ divisor = quotient divisor )dividend 4/17/2017 Dividing Decimals Dividend ÷ divisor = quotient divisor )dividend 111.384 ÷ 4.76 = 23.4 12