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1. 4-1 Estimate with Decimals Course 2 Warm Up Problem of the Day Lesson Presentation

2. 4-1 Estimate with Decimals Course 2 Warm Up Estimate. 1. 27 • 30 2.85• 92 3. 12 • 28 4. 185 • 201 900 8,100 300 40,000

3. 4-1 Estimate with Decimals Course 2 Problem of the Day I am a two-digit decimal greater than 0.25 and less than . My hundredths digit is 3 times my tenths digit. What number am I? 2 5 0.26 or 0.39

4. 4-1 Estimate with decimals Course 2 Learn to estimate decimal sums, differences, products, and quotients.

5. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here Vocabulary compatible numbers

6. 4-1 Estimate with Decimals Course 2 Jessie earned $27.00 for baby-sitting. She wants to use the money to buy a ticket to a water park for $14.75 and a souvenir T-shirt for $13.20. To find out if Jessie has enough money to buy both items, you can use estimation. To estimate the total cost of the ticket and the T-shirt, round each price to the nearest dollar, or integer. Then add the rounded values.

7. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here $14.75 7 7 > 5, so round to $15 $15 $13 $13.20 2 2 < 5, so round to $13 + $28 The estimated cost is $28, so Jessie does not have enough money to buy both items. To estimate decimal sums and differences, round each decimal to the nearest integer and then add or subtract.

8. 4-1 Estimate with Decimals Remember! To round to the nearest integer, look at the digit in the tenths place. If it is greater than or equal to 5, round to the next integer. If it is less than 5, keep the same integer. Course 2 Insert Lesson Title Here

9. 4-1 Estimate with Decimals 4.5 +8.9 +9 Course 2 Insert Lesson Title Here Additional Example 1A: Estimating Sums and Differences of Decimals Estimate by rounding to the nearest integer. A. 4.5 + 8.9 5 5 ≥ 5, so round to 5. 9 > 5, so round to 9. Estimate 14

10. 4-1 Estimate with Decimals 28.3 –11.7 –12 Course 2 Insert Lesson Title Here Additional Example 1B: Estimating Sums and Differences of Decimals Estimate by rounding to the nearest integer. B. 28.3 – 11.7 28 3 < 5, so round to 28. 7 > 5, so round to 12. Estimate 16

11. 4-1 Estimate with Decimals 57.2 + (–24) + (–23.72) Course 2 Insert Lesson Title Here Additional Example 1C: Estimating Sums and Differences of Decimals Estimate by rounding to the nearest integer. C. 57.2 + (–23.72) 57 2 < 5, so round to 57. 7 > 5, so round to –24. 33 Estimate

12. 4-1 Estimate with Decimals 6.8 +4.9 +5 Course 2 Insert Lesson Title Here Try This: Example 1A Estimate by rounding to the nearest integer. A. 6.7 + 4.9 7 8 ≥ 5, so round to 7. 9 > 5, so round to 5. Estimate 12

13. 4-1 Estimate with Decimals 19.2 –13.6 –14 Course 2 Insert Lesson Title Here Try This: Example 1B Estimate by rounding to the nearest integer. B. 19.2 – 13.6 19 2 < 5, so round to 19. 6 > 5, so round to –14. Estimate 5

14. 4-1 Estimate with Decimals 61.3 + (–19) + (–18.84) Course 2 Insert Lesson Title Here Try This: Example 1C Estimate by rounding to the nearest integer. C. 61.3 + (–18.84) 61 3 < 5, so round to 61. 8 > 5, so round to –19. 42 Estimate

15. 4-1 Estimate with Decimals Course 2 You can use compatible numbers when estimating. Compatiblenumbers are numbers that replace the numbers in the problem and are easier to use.

16. 4-1 Insert Lesson Title Here Course 2

17. 4-1 Estimate with Decimals 45.99  2.31  2 Course 2 Insert Lesson Title Here Additional Example 2A: Estimating with Decimals Use compatible numbers to estimate. A. 45.99 · 2.31 Round to the nearest multiple of 10. 50 3 < 5, so round to 2. 100 Estimate

18. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here Additional Example 2B: Estimating with Decimals Use compatible numbers to estimate. B. 51.33 ÷ (–7.98) 51 is prime, so round to 49. 51.33 49 –7.98 –7 divides into 49 without a remainder. –7 49 ÷ –7 = –7 Estimate

19. 4-1 Estimate with Decimals 39.62  4.99  5 Course 2 Insert Lesson Title Here Try This: Example 2A Use compatible numbers to estimate. A. 39.62 · 4.99 Round to the nearest multiple of 10. 40 9 > 5, so round to 5. 200 Estimate

20. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here Try This: Example 2B Use compatible numbers to estimate. B. 19.42 ÷ (–4.88) 19 is prime, so round to 20. 19.42 20 –4.88 –5 divides into 20 without a remainder. –5 20 ÷ –5 = –4 Estimate

21. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here Additional Example 3: Application Cara spent $58.80 on 4.8 pounds of lobster and calculated that she spent about $12 per pound of lobster. Use estimation to check whether her calculation is reasonable. $60 $58.80 Round to the nearest multiple of 10. 8 > 5, so round to 5. 5 4.85 60 ÷ 5 = 12 Estimate The estimate is the same as Cara’s calculation. The lobster cost about $12 per pound.

22. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here Try This: Example 3 Clem spent $18.43 on 11.7 pounds of apples. Is it reasonable to say that Clem spent about $2 per pound on apples? Round to the nearest multiple of 10. $20 18.43 10 divides evenly into 20 without a remainder. 10 11.7 20 ÷ 10 = 2 Estimate The estimate is the same as Clem’s calculation. The apples cost about $2 per pound.

23. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here Lesson Quiz: Part 1 Estimate by rounding to nearest integer. 1. 68.4 + 29.5 2. 7.24 + (–10.5) Use compatible numbers to estimate. 3. 48.27  4.67 4. 54.37  5.67 98 –4 Possible answers: 250 9

24. 4-1 Estimate with Decimals Course 2 Insert Lesson Title Here Lesson Quiz: Part 2 Use compatible numbers to estimate. 5. Ray is catering a party for 60 people. He needs to have 30 pounds of potato salad. He has made 6.21 pounds and 22.68 pounds. Does he have enough for the party? no