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

Warm Up Estimate , Course Estimate with Decimals 40,000

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? 0.26 or 0.39 Course Estimate with Decimals 5 2

Learn to estimate decimal sums, differences, products, and quotients. Course Estimate with decimals

Vocabulary compatible numbers Insert Lesson Title Here Course Estimate with Decimals

Course Estimate with Decimals 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 $ 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.

Insert Lesson Title Here Course Estimate with Decimals $ > 5, so round to $15$15 $ < 5, so round to $13 $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.

Insert Lesson Title Here 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. Remember! Course Estimate with Decimals

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

Insert Lesson Title Here Course Estimate with Decimals Estimate by rounding to the nearest integer. B – < 5, so round to > 5, so round to – Estimate –12 Additional Example 1B: Estimating Sums and Differences of Decimals

Insert Lesson Title Here Course Estimate with Decimals Estimate by rounding to the nearest integer. C (–23.72) 572 < 5, so round to > 5, so round to – (–23.72) 33Estimate + (–24) Additional Example 1C: Estimating Sums and Differences of Decimals

Insert Lesson Title Here Course Estimate with Decimals Estimate by rounding to the nearest integer. A ≥ 5, so round to 7. 9 > 5, so round to Estimate +5 Try This: Example 1A

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

Insert Lesson Title Here Course Estimate with Decimals Estimate by rounding to the nearest integer. C (–18.84) 613 < 5, so round to > 5, so round to – (–18.84) 42Estimate + (–19) Try This: Example 1C

Compatible numbers are numbers that replace the numbers in the problem and are easier to use. Course Estimate with Decimals You can use compatible numbers when estimating.

Course Insert Lesson Title Here Guidelines for Using Compatible Numbers When multiplying... round numbers to the nearest nonzero integer or to numbers that are easy to multiply. When dividing... round numbers so that they divide without leaving a remainder.

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

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

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

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

Insert Lesson Title Here Course Estimate with Decimals 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. $58.80 $60 Round to the nearest multiple of Estimate Additional Example 3: Application 60 ÷ 5 = 12 8 > 5, so round to 5. The estimate is the same as Cara’s calculation. The lobster cost about $12 per pound.

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

Lesson Quiz: Part 1 Estimate by rounding to nearest integer (–10.5) Use compatible numbers to estimate   5.67 –4 98 Insert Lesson Title Here Course Estimate with Decimals Possible answers:

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 pounds. Does he have enough for the party? Insert Lesson Title Here Course Estimate with Decimals no