3.2 Estimating Decimal Products and Quotients

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Presentation transcript:

3.2 Estimating Decimal Products and Quotients Mr. Phillips Intro to Algebra

Lesson Objectives By the end of today’s lesson you will be able to: Estimate products using mental math. Estimate quotients using compatible numbers.

Estimating Products Example #1 (pg. 132) Estimate each product. 1) 7.65 × 3.2 2) 6.43 × 4.7

Estimating Products OYO #1 Estimate each product. 3) 4.56×7.02 4) 6.3×9.2 5) 3.29×58 ≈ 35 ≈ 54 ≈180

Estimating Products Example #2 (pg. 132) Josh bought 3 yards of fabric to make a flag. Fabric costs $5.35 per yard. The clerk says his total is $14.95 before tax. Did the clerk make a mistake?

Estimating Products OYO #2 You buy 24 donuts from the Donut Emporium in Plano. Each donut costs $.98 . Estimate the cost before tax for 2 dozen donuts? ≈ $24

Objective #1 Can you… ~ estimate products using mental math? Let’s Check…

Check for Understanding Do problems 11, 13, 15 on Practice Worksheet 3- 2. Next, compare answers with a neighbor. ≈54 13) ≈600 15) ≈1440

Estimating Quotients 6 ÷ 3 = 2 The first number is the dividend. The second number is the divisor. The number after the = sign is the quotient.

Estimating Quotients Name the following: 18 ÷3 = 6 3 is the: 18 is the: 6 is the:

Estimating Quotients defn: compatible numbers: -numbers easy to divide mentally *When dividing, you can use compatible numbers to estimate quotients

Estimating Quotients When you estimate the quotient: Round the divisor. Round the dividend to a compatible number.

Estimating Quotients Example #3 (pg. 133) Estimate the quotient using compatible numbers. 1) 14.9 ÷ 2.8 2) 25.3 ÷ 4.9

Estimating Quotients OYO #3 Estimate the quotient using compatible numbers. 3) 35.8÷3.8 4) 29.4÷1.8 5) 49.6÷4.4 ≈ 9 ≈ 15 ≈ 10

Estimating Quotients Example #4 (pg. 133) The cost to ship 1 yearbook is $3.12. The total cost for a shipment was $62.40. Estimate how many books were in the shipment. Round the divisor. Round to a multiple of 3. Find the quotient.

Estimating Quotients Example #5 (pg. 133) Use estimation. Is each quotient reasonable? 1) 17.931÷8.34 =2.15 2) 31.423÷5.94=3.29

Estimating Quotients OYO #5 Use estimation. Is each quotient reasonable? 3) 318.274÷4.07=78.2 4) 41.09÷6.88=5.12 Reasonable Not Reasonable

Objective #2 Can you… ~ estimate quotients using compatible numbers? Let’s Check…

Check for Understanding Do problems 18, 19, 21 on Practice Worksheet 3- 2. Next, compare answers with a neighbor. 18) ≈5 19) ≈6 21) ≈15

3.2 Estimating Decimal Products and Quotients Ask yourself if you can do the following: Estimate products using mental math. Estimate quotients using compatible numbers. Homework: 3.2 on the assignment sheet