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Copyright © 2010 Pearson Education, Inc. All rights reserved Sec 5.2 - 1 5.2 Rounding Decimal Numbers Chapter 5 Rational Numbers: Positive and Negative Decimals Copyright © 2010 Pearson Education, Inc. All rights reserved Sec 5.2 - 2 5.2 Rounding Decimal Numbers Objectives 1. Learn the rules for rounding decimals. 2. Round decimals to any given place. 3. Round money amounts to the nearest cent or nearest dollar. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 3 Objective 1: Learn the rules for rounding decimals. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 4 Objective 2: Round decimals to any given place. Example Round 14.39652 to the nearest thousandth. Is it closer to 14.396 or to 14.397? Step 1 Draw a “cut-off ” line after the thousandths place. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 5 Objective 2: Round decimals to any given place. Example (continued) Step 2 Look only at the first digit you are cutting off. Ignore the other digits you are cutting off. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 6 Objective 2: Round decimals to any given place. Example (continued) Step 3 If the first digit you are cutting off is 5 or more, round up the part of the number you are keeping. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 7 Objective 2: Identify the place value of a digit. Decimal places are the number of digits to the right of the decimal point. 14.397 has three decimal places. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 8 Objective 2: Round decimals to any given place. Example Round 5.3496 to the nearest tenth. Is it closer to 5.3 or to 5.4? Step 1 Draw a “cut-off ” line after the tenths place. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 9 Objective 2: Round decimals to any given place. Example (continued) Step 2 Step 3 5.3469 rounded to the nearest tenth is 5.3. You may write 5.3469 ≈ 5.3. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 10 Objective 2: Round decimals to any given place. Example Round 0.69738 to the nearest hundredth. Is it closer to 0.69 or 0.70? Step 1 Draw a “cut-off ” line after the hundredths place. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 11 Objective 2: Round decimals to any given place. Example (continued) Step 2 Step 3 Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 12 Objective 2: Round decimals to any given place. Example (continued) 0.69738 rounded to the nearest hundredth is 0.70. You must write the 0 in the hundredths place. You may write 0.69738 ≈ 0.70. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 13 Objective 2: Round decimals to any given place. Example Round 0.01806 to the nearest thousandth. Is it closer to 0.018 or 0.019? Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 14 Objective 3: Round money amounts to the nearest cent or nearest dollar. Example Round $2.4238 to the nearest cent. Is it closer to $2.42 or $2.43? $2.4238 rounds to $2.42. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 15 Objective 3: Round money amounts to the nearest cent or nearest dollar. Example Round $0.695 to the nearest cent. Is it closer to $0.69 or $0.70? $0.695 rounds to $0.70. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 16 Objective 3: Round money amounts to the nearest cent or nearest dollar. Example Round $48.69 to the nearest dollar. Is it closer to $48 or $49? $48.69 rounds to $49. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 17 Objective 3: Round money amounts to the nearest cent or nearest dollar. Example Round $594.36 to the nearest dollar. Is it closer to $594 or $595? $594.36 rounds to $594. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 18 Objective 3: Round money amounts to the nearest cent or nearest dollar. Example Round $399.88 to the nearest dollar. Is it closer to $399 or $400? $399.88 rounds to $400. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 19 Objective 3: Round money amounts to the nearest cent or nearest dollar. Example Round $0.61 to the nearest dollar. Is it closer to $0 or $1? $0.61 rounds to $1. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 5.2 - 20