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# 3.4 rounding decimals

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### 3.4 rounding decimals

1. 1. 3.4 Rounding Decimals<br />October 1, 2010<br />
2. 2. For you notebook (copy this):<br />Rounding Decimals: to round a decimal to a given place value, look at the digit in the place to the right.<br />If the digit is 4 or less, round down.<br />If the digit is 5 or greater, round up.<br />
3. 3. EXAMPLE 1<br />Using a Number Line to Round<br />Use a number line to round 3.87 to the nearest tenth.<br />
4. 4. EXAMPLE 1<br />Using a Number Line to Round<br />Use a number line to round 3.87 to the nearest tenth.<br />
5. 5. EXAMPLE 1<br />Using a Number Line to Round<br />Use a number line to round 3.87 to the nearest tenth.<br />ANSWER<br />
6. 6. EXAMPLE 1<br />Using a Number Line to Round<br />Use a number line to round 3.87 to the nearest tenth.<br />ANSWER<br />The decimal 3.87 rounds up to 3.9.<br />
7. 7. for Example 1<br />GUIDED PRACTICE<br />
8. 8. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />
9. 9. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />1. 1.3<br />
10. 10. 1 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1.9 2.0<br />for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />1. 1.3<br />
11. 11. 1 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1.9 2.0<br />for Example 1<br />GUIDED PRACTICE<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />1. 1.3<br />The decimal 1.3 iscloser to 1 than to 3<br />
12. 12. 1 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1.9 2.0<br />for Example 1<br />GUIDED PRACTICE<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />1. 1.3<br />The decimal 1.3 iscloser to 1 than to 3<br />ANSWER<br />The decimal 1.3 rounds down to 1.<br />
13. 13. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />2. 2.8<br />
14. 14. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />2. 2.8<br /> 2.2 2.3 2. 4 2. 5 2. 6 2. 7 2. 8 2. 9 3.0 <br />
15. 15. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />2. 2.8<br /> 2.2 2.3 2. 4 2. 5 2. 6 2. 7 2. 8 2. 9 3.0 <br />The decimal 2.8 is closer to 3 than to 2<br />
16. 16. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest one)<br />2. 2.8<br /> 2.2 2.3 2. 4 2. 5 2. 6 2. 7 2. 8 2. 9 3.0 <br />The decimal 2.8 is closer to 3 than to 2<br />ANSWER<br />The decimal 2.8 rounds up to 3.<br />
17. 17. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />3. 3.74<br />
18. 18. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />3. 3.74<br />hundredth<br />tenths<br />3. 6 3. 7 3. 8 3. 9<br />
19. 19. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />3. 3.74<br />hundredth<br />tenths<br />3. 6 3. 7 3. 8 3. 9<br />The decimal 3.74 is closer to 3.7 than to 3.8<br />
20. 20. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />3. 3.74<br />hundredth<br />tenths<br />3. 6 3. 7 3. 8 3. 9<br />The decimal 3.74 is closer to 3.7 than to 3.8<br />ANSWER<br />The decimal 3.74 rounds down to 3.7.<br />
21. 21. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />4. 3.86<br />
22. 22. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />4. 3.86<br />tenths<br />hundredth<br />3. 6 3. 7 3. 8 3. 9 4. 0<br />
23. 23. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />4. 3.86<br />tenths<br />hundredth<br />3. 6 3. 7 3. 8 3. 9 4. 0<br />The decimal 3.86 is closer to 3.9 than to 3.8<br />
24. 24. for Example 1<br />GUIDED PRACTICE<br />Use a number line to round the decimal as specified.<br />(nearest tenth)<br />4. 3.86<br />tenths<br />hundredth<br />3. 6 3. 7 3. 8 3. 9 4. 0<br />The decimal 3.86 is closer to 3.9 than to 3.8<br />ANSWER<br />The decimal 3.86 rounds up to 3.9.<br />
25. 25. Rounding Decimals (write these examples in your notebook.)<br />Round the decimal to the place value of the yellow digit.<br />3.23 ------> 3.2, The digit to the right of 2 is 3, so round down.<br />6.485 ------> 6.49, The digit to the right of 8 is 5, so round up.<br />2.83619 -----> 2. 836, The digit to the right of the 6 is 1, so round down.<br />5.961 -----> 6.0, The digit to the right of 9 is 6, so round up. This causes the 5 to become a 6.<br />
26. 26. Now you try:<br />Round to the decimal as specified:<br />5.29 (nearest tenth)<br />7.096 (nearest hundredth)<br />6.48 (nearest one)<br />3.9876 (nearest thousandth)<br />
27. 27. Check your answers:<br />Round to the decimal as specified:<br />5.29 (nearest tenth) 5.3<br />7.096 (nearest hundredth) 7.10<br />6.48 (nearest one) 6<br />3.9876 (nearest thousandth) 3.988<br />
28. 28. Write this in your notebook:<br />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.<br />
29. 29. Rounding to the Leading Digit (you do not need to copy this)<br />A guitar was created that is 0.0003937 inch long. Round the length of the guitar to the place value of the leading digit.<br />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. <br />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.<br />Answer the length rounded to the leading digit is 0.0004 inch. <br />
30. 30. Try these (in your notebook)<br />Round the decimal to the leading digit<br />0.058<br />0.0091<br />0.0952<br />0.006192<br />
31. 31. Check your answers.<br />Round the decimal to the leading digit<br />0.058 0.06<br />0.0091 0.009<br />0.0952 0.10 (you don’t have to have the last 0)<br />0.006192 0.006<br />
32. 32. When you finish this slideshow:<br />Take the section quiz (as practice) on classzone.com. Go to assessments, then click on section quizzes. Then click on 3.4 Rounding Decimals.<br />Then play the animated math game on classzone.com. Go to animated math. Then click on Chapter 3: Comparing, Ordering and Rounding Decimals.<br />