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Warm-Up • Evaluate the Expression (5 2 3 4 ) 3 2 1 2 Comparing, Ordering and Rounding Decimals 2.1 Vocabulary • Decimal – a number that is written using the base-ten place value system where a decimal point separates the ones’ and the tenths’ digits. • Place Value – The place value of each digit in a number depends on its position within the number. Decimal Notes • Digits can be placed to the left and right of a decimal point, to indicate numbers greater than one or less than one. • The decimal point helps us to keep track of where the ones (units) place is. The decimal is placed just to the right of the ones place. As you move right from the decimal point, each place value is divided by 10. Decimals and Place Values Decimal Point Using “and” Example • What is the place value of the underlined number 35.243? hundredths Example • What is the value of the underlined number 14.6673? seven thousandths Comparing Decimals • How to Compare Decimals – Write the numbers in a column, lining up the decimal points and makes the numbers have the same place value by using zeros. Then compare from left to right. Example • Which number is greater? 5.702 5.71 5.71 Example • At Jason’s 6-month checkup, he weighed 15.2 pounds. At Ali’s 6-month checkup, she weighed 15.08 pounds. Compare the weights of the babies to determine who weighed more. 15.20 lb Jason 15.08 lb Ali You Try! • Copy and complete the statement using <, >, or =. 15.09 15.3 _?_ Example • Order 2.11, 2.21, 2, 2.06, and 2.24 from least to greatest. From least to greatest, the numbers are 2, 2.06, 2.11, 2.21, and 2.24. Interactive Animation • Comparing Decimals You Try! • Order 3.84, 4.4, 4.83, 3.48 & 4.38 from least to greatest. 3.48, 3.84, 4.38, 4.4, 4.83 Rounding Decimals To round a decimal to a given place value, look at the digit in the place to the right. • If the digit is less than 5, round down. • If the digit is 5 or greater, round up. EXAMPLE 3 Rounding a Decimal • Round 7.126 to the nearest tenth. You want to round to the nearest tenth. 7.126 ANSWER Because the hundredths’ digit is less than 5, round down and drop the remaining digits. The decimal 7.126 rounded to the nearest tenth is 7.1. Example • Round the number to the nearest hundredth. 34.0152 34.02 You Try! • Round the number to the nearest hundredth. 1.5034 1.50 Assignment Page 58, Chapter 2.1 # 5-13 odd, 35, 39, 41, 45 Extension Mixed Review #46-52