1 Chapter Chapter 2 The Whole Numbers

Rounding and Estimating Section 1.5 Rounding and Estimating

Rounding Whole Numbers Rounding a whole number means approximating it. 26 is closer to 30 than 20, so 26 is rounded to the nearest ten is 30. 52 is closer to 50 than 60, so 52 is rounded to the nearest ten is 50.

Rounding Whole Numbers 25 is halfway between 20 and 30. It is not closer to either number. In such a case, we round to the larger ten, that is, to 30.

Rounding Whole Numbers Rounding Whole Numbers to a Given Place Value Step 1: Locate the digit to the right of the given place value. Step 2: If this digit is 5 or greater, add 1 to the digit in the given place value and replace each digit to its right by 0. Step 3: If this digit is less than 5, replace it and each digit to its right by 0.

Example 568 rounds to 570 Round 568 to the nearest ten. 5 6 8 5 6 8 The digit to the right of the tens place is the ones place, which is circled. tens place Since the circled digit is 5 or greater, add 1 to the 6 in the tens place and replace the digit to the right by 0. 568 rounds to 570

Examples Round to the nearest ten. a. 57 b. 641 c. 325

Examples Round 278,362 to the nearest thousand. 2 7 8, 3 6 2 3 is less than 5, do not add 1 thousandsplace Replace with zeros. 278,362 rounds to 278,000

Examples Round to the nearest thousand. a. 77,304 b. 9222 c. 671,800

Examples Round 248,982 to the nearest hundred. 2 4 8, 9 8 2 8 is greater than or equal to 5 hundredsplace Add 1 248,982 rounds to 249,000

Examples Round to the nearest hundred. a. 3474 b. 76,243 c. 978,965

Estimating Sums and Differences Estimate the sum by rounding each number to the nearest hundred. Example Objective B

Solving Problems by Estimating Example Jared Nuss scored 89, 92, 100, 67, 75 and 89 on his biology tests. Round each score to the nearest ten to estimate his total score. Objective C

Example Tasha Kilbey is trying to estimate how far it is from Gove, Kansas, to Hays, Kansas. Round each given distance on the map to the nearest ten to estimate the total distance. The actual distances: 11 miles 16 miles 19 miles 31 miles Objective C

Example In 2010, there were 15,427 reported cases of chicken pox, 2612 reported cases of mumps, and 27,550 reported cases of pertussis (whooping cough). Round each number to the nearest thousand to estimate the total number of cases reported for these preventable diseases. (Source: Centers for Disease Control and Prevention) 15,427 chicken pox 2612 mumps 27,550 pertussis Objective C