1. 1
Chapter
Chapter 2
The Whole Numbers

2. Rounding and Estimating
Section
1.5
Rounding and Estimating

3. 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.

4. 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.

5. 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.

6. Example 568 rounds to 570 Round 568 to the nearest ten. 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

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

8. 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

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

10. 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

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

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

13. 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

14. 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

15. 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