Learn on PengiIllustrative Mathematics, Grade 5Chapter 4: Wrapping Up Multiplication and Division with Multi-Digit Numbers

Lesson 8: Partial Quotients: Strategy and Algorithm

In this Grade 5 lesson from Illustrative Mathematics Chapter 4, students learn to divide multi-digit whole numbers using the partial quotients strategy by applying place value understanding and the relationship between multiplication and division. Students explore how a dividend can be decomposed in different ways to produce partial quotients, comparing approaches that use multiplication expressions versus division expressions to reach the same result. The lesson emphasizes choosing decompositions that can be calculated mentally, building efficiency with the partial quotients algorithm.

Section 1

Using Partial Quotients to Record Sharing

Property

The partial quotients algorithm is a method for recording the steps of sharing division.
Each time you share a place value, you record the result as a partial quotient.
The amount shared is multiplied by the divisor and subtracted from the dividend to find what remains to be divided.

Examples

Section 2

Estimate Partial Quotients Using Multiples of 10

Property

To estimate the quotient when dividing by a multiple of 10, use basic division facts. Think of the dividend and divisor in terms of tens.
For example, to solve 84÷2084 \div 20, you can think of it as 8 tens÷2 tens8 \text{ tens} \div 2 \text{ tens}, which simplifies to 8÷28 \div 2.

Examples

  • To estimate 72÷3072 \div 30, think: How many 3s are in 7? The answer is 2. So, 72÷30272 \div 30 \approx 2. (60÷30=260 \div 30 = 2)
  • To estimate 154÷50154 \div 50, think: How many 5s are in 15? The answer is 3. So, 154÷503154 \div 50 \approx 3. (150÷50=3150 \div 50 = 3)
  • To estimate 430÷60430 \div 60, think: How many 6s are in 43? The answer is 7. So, 430÷607430 \div 60 \approx 7. (420÷60=7420 \div 60 = 7)

Explanation

Estimating helps you find an answer that is close to the exact quotient before you start long division. By using basic facts, you can simplify the problem and make a reasonable guess. This strategy is useful for determining the first digit of your quotient in the standard algorithm. It also helps you check if your final answer makes sense.

Section 3

Divide Whole Numbers Using Partial Quotients

Property

Partial quotients is a method for solving division problems by repeatedly subtracting "friendly" multiples of the divisor from the dividend.
The final quotient is the sum of all the partial quotients.

Examples

Book overview

Jump across lessons in the current chapter without opening the full course modal.

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Chapter 4: Wrapping Up Multiplication and Division with Multi-Digit Numbers

  1. Lesson 1

    Lesson 1: Estimate and Find Products

  2. Lesson 2

    Lesson 2: Partial Products: Diagrams and Algorithms

  3. Lesson 3

    Lesson 3: Standard Algorithm: Introduction and Practice

  4. Lesson 4

    Lesson 4: Standard Algorithm: Multi-digit Numbers with Composing

  5. Lesson 5

    Lesson 5: Build Multiplication Fluency

  6. Lesson 6

    Lesson 6: The Birds

  7. Lesson 7

    Lesson 7: World's Record Folk Dance

  8. Lesson 8Current

    Lesson 8: Partial Quotients: Strategy and Algorithm

  9. Lesson 9

    Lesson 9: Practice Division with Partial Quotients

  10. Lesson 10

    Lesson 10: Find Missing Side Lengths

  11. Lesson 11

    Lesson 11: World's Record Noodle Soup

  12. Lesson 12

    Lesson 12: Fractions as Partial Quotients (Optional)

  13. Lesson 13

    Lesson 13: Lots of Milk

  14. Lesson 14

    Lesson 14: Real-World Applications: Trash Problems

Lesson overview

Expand to review the lesson summary and core properties.

Expand

Section 1

Using Partial Quotients to Record Sharing

Property

The partial quotients algorithm is a method for recording the steps of sharing division.
Each time you share a place value, you record the result as a partial quotient.
The amount shared is multiplied by the divisor and subtracted from the dividend to find what remains to be divided.

Examples

Section 2

Estimate Partial Quotients Using Multiples of 10

Property

To estimate the quotient when dividing by a multiple of 10, use basic division facts. Think of the dividend and divisor in terms of tens.
For example, to solve 84÷2084 \div 20, you can think of it as 8 tens÷2 tens8 \text{ tens} \div 2 \text{ tens}, which simplifies to 8÷28 \div 2.

Examples

  • To estimate 72÷3072 \div 30, think: How many 3s are in 7? The answer is 2. So, 72÷30272 \div 30 \approx 2. (60÷30=260 \div 30 = 2)
  • To estimate 154÷50154 \div 50, think: How many 5s are in 15? The answer is 3. So, 154÷503154 \div 50 \approx 3. (150÷50=3150 \div 50 = 3)
  • To estimate 430÷60430 \div 60, think: How many 6s are in 43? The answer is 7. So, 430÷607430 \div 60 \approx 7. (420÷60=7420 \div 60 = 7)

Explanation

Estimating helps you find an answer that is close to the exact quotient before you start long division. By using basic facts, you can simplify the problem and make a reasonable guess. This strategy is useful for determining the first digit of your quotient in the standard algorithm. It also helps you check if your final answer makes sense.

Section 3

Divide Whole Numbers Using Partial Quotients

Property

Partial quotients is a method for solving division problems by repeatedly subtracting "friendly" multiples of the divisor from the dividend.
The final quotient is the sum of all the partial quotients.

Examples

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 4: Wrapping Up Multiplication and Division with Multi-Digit Numbers

  1. Lesson 1

    Lesson 1: Estimate and Find Products

  2. Lesson 2

    Lesson 2: Partial Products: Diagrams and Algorithms

  3. Lesson 3

    Lesson 3: Standard Algorithm: Introduction and Practice

  4. Lesson 4

    Lesson 4: Standard Algorithm: Multi-digit Numbers with Composing

  5. Lesson 5

    Lesson 5: Build Multiplication Fluency

  6. Lesson 6

    Lesson 6: The Birds

  7. Lesson 7

    Lesson 7: World's Record Folk Dance

  8. Lesson 8Current

    Lesson 8: Partial Quotients: Strategy and Algorithm

  9. Lesson 9

    Lesson 9: Practice Division with Partial Quotients

  10. Lesson 10

    Lesson 10: Find Missing Side Lengths

  11. Lesson 11

    Lesson 11: World's Record Noodle Soup

  12. Lesson 12

    Lesson 12: Fractions as Partial Quotients (Optional)

  13. Lesson 13

    Lesson 13: Lots of Milk

  14. Lesson 14

    Lesson 14: Real-World Applications: Trash Problems