This document provides instructions on rounding decimals to a specified place value. It explains that when rounding, if the digit to the right of the specified place value is 4 or less, round down, and if it is 5 or greater, round up. Examples are provided rounding decimals to the nearest tenth, hundredth, and thousandth using number lines. Practice problems are also included for students to round decimals on their own.

1. 3.4 Rounding Decimals October 1, 2010

2. For you notebook (copy this): 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 4 or less, round down. If the digit is 5 or greater, round up.

3. EXAMPLE 1 Using a Number Line to Round Use a number line to round 3.87 to the nearest tenth.

4. EXAMPLE 1 Using a Number Line to Round Use a number line to round 3.87 to the nearest tenth.

5. EXAMPLE 1 Using a Number Line to Round Use a number line to round 3.87 to the nearest tenth. ANSWER

6. EXAMPLE 1 Using a Number Line to Round Use a number line to round 3.87 to the nearest tenth. ANSWER The decimal 3.87 rounds up to 3.9.

7. for Example 1 GUIDED PRACTICE

8. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified.

9. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 1. 1.3

10. 1 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1.9 2.0 for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 1. 1.3

11. 1 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1.9 2.0 for Example 1 GUIDED PRACTICE GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 1. 1.3 The decimal 1.3 iscloser to 1 than to 3

12. 1 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1.9 2.0 for Example 1 GUIDED PRACTICE GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 1. 1.3 The decimal 1.3 iscloser to 1 than to 3 ANSWER The decimal 1.3 rounds down to 1.

13. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 2. 2.8

14. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 2. 2.8 2.2 2.3 2. 4 2. 5 2. 6 2. 7 2. 8 2. 9 3.0

15. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 2. 2.8 2.2 2.3 2. 4 2. 5 2. 6 2. 7 2. 8 2. 9 3.0 The decimal 2.8 is closer to 3 than to 2

16. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest one) 2. 2.8 2.2 2.3 2. 4 2. 5 2. 6 2. 7 2. 8 2. 9 3.0 The decimal 2.8 is closer to 3 than to 2 ANSWER The decimal 2.8 rounds up to 3.

17. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 3. 3.74

18. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 3. 3.74 hundredth tenths 3. 6 3. 7 3. 8 3. 9

19. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 3. 3.74 hundredth tenths 3. 6 3. 7 3. 8 3. 9 The decimal 3.74 is closer to 3.7 than to 3.8

20. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 3. 3.74 hundredth tenths 3. 6 3. 7 3. 8 3. 9 The decimal 3.74 is closer to 3.7 than to 3.8 ANSWER The decimal 3.74 rounds down to 3.7.

21. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 4. 3.86

22. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 4. 3.86 tenths hundredth 3. 6 3. 7 3. 8 3. 9 4. 0

23. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 4. 3.86 tenths hundredth 3. 6 3. 7 3. 8 3. 9 4. 0 The decimal 3.86 is closer to 3.9 than to 3.8

24. for Example 1 GUIDED PRACTICE Use a number line to round the decimal as specified. (nearest tenth) 4. 3.86 tenths hundredth 3. 6 3. 7 3. 8 3. 9 4. 0 The decimal 3.86 is closer to 3.9 than to 3.8 ANSWER The decimal 3.86 rounds up to 3.9.

25. Rounding Decimals (write these examples in your notebook.) Round the decimal to the place value of the yellow digit. 3.23 ------> 3.2, The digit to the right of 2 is 3, so round down. 6.485 ------> 6.49, The digit to the right of 8 is 5, so round up. 2.83619 -----> 2. 836, The digit to the right of the 6 is 1, so round down. 5.961 -----> 6.0, The digit to the right of 9 is 6, so round up. This causes the 5 to become a 6.

26. Now you try: Round to the decimal as specified: 5.29 (nearest tenth) 7.096 (nearest hundredth) 6.48 (nearest one) 3.9876 (nearest thousandth)

27. Check your answers: Round to the decimal as specified: 5.29 (nearest tenth) 5.3 7.096 (nearest hundredth) 7.10 6.48 (nearest one) 6 3.9876 (nearest thousandth) 3.988

28. Write this in your notebook: Rounding Small Numbers: You can round a very small number to the place value of its leading digit to help make it easier to understand. In a decimal, the leading digit is the first nonzero digit as you read from left to right.

29. Rounding to the Leading Digit (you do not need to copy this) A guitar was created that is 0.0003937 inch long. Round the length of the guitar to the place value of the leading digit. To Solve: The first nonzero digit as you read 0.0003937 from left to right is 3 and it is in the ten-thousandths place. You should round the digit to the nearest ten thousandth. Because 9 is to the right of the ten-thousandth’s place, round 3 up to 4. Answer the length rounded to the leading digit is 0.0004 inch.

30. Try these (in your notebook) Round the decimal to the leading digit 0.058 0.0091 0.0952 0.006192

31. Check your answers. Round the decimal to the leading digit 0.058 0.06 0.0091 0.009 0.0952 0.10 (you don’t have to have the last 0) 0.006192 0.006

32. When you finish this slideshow: Take the section quiz (as practice) on classzone.com. Go to assessments, then click on section quizzes. Then click on 3.4 Rounding Decimals. Then play the animated math game on classzone.com. Go to animated math. Then click on Chapter 3: Comparing, Ordering and Rounding Decimals.