Learn on PengiPengi Math (Grade 4)Chapter 6: Understanding Fractions

Lesson 4: Decomposition, Mixed Numbers, and Improper Fractions

In this Grade 4 lesson from Pengi Math Chapter 6, students learn how to decompose fractions into sums of unit fractions, convert between improper fractions and mixed numbers, and model these concepts using tape diagrams. Students practice multiplication strategies to rewrite mixed numbers as improper fractions and develop comparison skills by analyzing whole number and fractional parts separately.

Section 1

Composing Fractions with Unit Fractions

Property

Any fraction ab\frac{a}{b} is the sum of 'a' unit fractions of size 1b\frac{1}{b}.

ab=1b+1b++1ba times\frac{a}{b} = \underbrace{\frac{1}{b} + \frac{1}{b} + \dots + \frac{1}{b}}_{a \text{ times}}

Section 2

Decomposing the Whole (1) into Unit Fractions

Property

The number 1 can be expressed as a fraction nn\frac{n}{n} and decomposed into a sum of nn unit fractions.

1=nn=1n+1n++1nn times1 = \frac{n}{n} = \underbrace{\frac{1}{n} + \frac{1}{n} + \dots + \frac{1}{n}}_{n \text{ times}}

Examples

Section 3

Decompose a Fraction into a Sum of Fractions

Property

A fraction ab\frac{a}{b} can be decomposed into a sum of smaller fractions with the same denominator, such as ab=xb+yb\frac{a}{b} = \frac{x}{b} + \frac{y}{b}, where x+y=ax + y = a.

Examples

Section 4

Decompose a Fraction Using Subtraction

Property

A fraction can be decomposed as the difference between two other fractions with the same denominator. For a fraction ac\frac{a}{c}, we can find fractions bc\frac{b}{c} and dc\frac{d}{c} such that:

ac=bcdc\frac{a}{c} = \frac{b}{c} - \frac{d}{c}

where bd=ab - d = a.

Examples

  • 38=5828\frac{3}{8} = \frac{5}{8} - \frac{2}{8}
  • 75=10535\frac{7}{5} = \frac{10}{5} - \frac{3}{5}
  • 12=112\frac{1}{2} = 1 - \frac{1}{2}

Explanation

Decomposing a fraction means breaking it into parts. While we often think of this as adding smaller fractions together, we can also express a fraction as a subtraction problem. This involves finding a larger fraction and subtracting another fraction from it to get the original amount. This method helps build a flexible understanding of fraction relationships and operations.

Book overview

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Chapter 6: Understanding Fractions

  1. Lesson 1

    Lesson 1: The Unit Fraction Concept

  2. Lesson 2

    Lesson 2: Understanding and Generating Equivalent Fractions

  3. Lesson 3

    Lesson 3: Strategies for Comparing Fractions

  4. Lesson 4Current

    Lesson 4: Decomposition, Mixed Numbers, and Improper Fractions

Lesson overview

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Section 1

Composing Fractions with Unit Fractions

Property

Any fraction ab\frac{a}{b} is the sum of 'a' unit fractions of size 1b\frac{1}{b}.

ab=1b+1b++1ba times\frac{a}{b} = \underbrace{\frac{1}{b} + \frac{1}{b} + \dots + \frac{1}{b}}_{a \text{ times}}

Section 2

Decomposing the Whole (1) into Unit Fractions

Property

The number 1 can be expressed as a fraction nn\frac{n}{n} and decomposed into a sum of nn unit fractions.

1=nn=1n+1n++1nn times1 = \frac{n}{n} = \underbrace{\frac{1}{n} + \frac{1}{n} + \dots + \frac{1}{n}}_{n \text{ times}}

Examples

Section 3

Decompose a Fraction into a Sum of Fractions

Property

A fraction ab\frac{a}{b} can be decomposed into a sum of smaller fractions with the same denominator, such as ab=xb+yb\frac{a}{b} = \frac{x}{b} + \frac{y}{b}, where x+y=ax + y = a.

Examples

Section 4

Decompose a Fraction Using Subtraction

Property

A fraction can be decomposed as the difference between two other fractions with the same denominator. For a fraction ac\frac{a}{c}, we can find fractions bc\frac{b}{c} and dc\frac{d}{c} such that:

ac=bcdc\frac{a}{c} = \frac{b}{c} - \frac{d}{c}

where bd=ab - d = a.

Examples

  • 38=5828\frac{3}{8} = \frac{5}{8} - \frac{2}{8}
  • 75=10535\frac{7}{5} = \frac{10}{5} - \frac{3}{5}
  • 12=112\frac{1}{2} = 1 - \frac{1}{2}

Explanation

Decomposing a fraction means breaking it into parts. While we often think of this as adding smaller fractions together, we can also express a fraction as a subtraction problem. This involves finding a larger fraction and subtracting another fraction from it to get the original amount. This method helps build a flexible understanding of fraction relationships and operations.

Book overview

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

Continue this chapter

Chapter 6: Understanding Fractions

  1. Lesson 1

    Lesson 1: The Unit Fraction Concept

  2. Lesson 2

    Lesson 2: Understanding and Generating Equivalent Fractions

  3. Lesson 3

    Lesson 3: Strategies for Comparing Fractions

  4. Lesson 4Current

    Lesson 4: Decomposition, Mixed Numbers, and Improper Fractions