Lesson Plan: Subtracting Fractions with Like Denominators

 

Lesson Summary

This 50-minute lesson focuses on teaching students how to subtract fractions with like denominators. Students will develop their conceptual understanding and procedural skills using a combination of hands-on activities, visual aids, and step-by-step instruction. Media4Math.com multimedia resources, such as tutorials and visual slideshows, will be incorporated throughout the lesson. The session concludes with a 10-question quiz to assess comprehension. An answer key is provided.

Lesson Objectives

  • Subtract fractions with like denominators.
  • Solve word problems involving subtraction of fractions with like denominators.

Common Core Standards

  • CCSS.Math.Content.4.NF.3.a: Understand addition and subtraction of fractions as joining and separating parts referring to the same whole.

Prerequisite Skills

  • Addition of fractions with like denominators.
  • Subtraction of whole numbers.

Key Vocabulary

Multimedia Resources

 

 

Warm Up Activities

Choose from one or more of these activities:

Calculator Activity

Use any fraction calculator for this activity. Desmos.com has a freely available calculator.

  1. Provide students with a set of fraction problems such as \( \frac{5}{7} - \frac{2}{7} \) or \( \frac{8}{9} - \frac{2}{9} \). Focus on fractions that result in a fraction in simplest form.
  2. Then have students subtract fractions whose difference needs to be simplified. Discuss how to go from the initial result and the simplified form by discussing common factors. 

 

FractionsFractions

 

Hands-On: Fraction Bars

Distribute fraction bars to small groups. Students use the bars to visually represent problems like \( \frac{6}{10} - \frac{4}{10} \) by physically removing pieces. Facilitate a discussion about the remaining pieces.

Refer to this booklet for printable fraction bars:

https://www.media4math.com/library/76897/asset-preview

 

Fractions

\( \frac{6}{10} - \frac{4}{10} \) = \( \frac{2}{10} \)

= \( \frac{1}{5} \)

 

Multimedia Visuals

Show Media4Math's visual models of fraction subtraction using pizza fractions. Ask students to explain how much pizza was consumed from Before to After.

Before

After

FractionsFractions
FractionsFractions
FractionsFractions

 

 

Teach

Explain that subtracting fractions with like denominators involves subtracting only the numerators while keeping the denominator constant. Reinforce this with examples and visual aids.

Key Concepts

  • Fractions must have the same denominators to be subtracted directly.
  • Subtract the numerators, leaving the denominator unchanged.
  • Simplify the fraction if possible.

Example 1: Simple Subtraction

Subtract: \( \frac{5}{8} - \frac{2}{8} \).

  • Use fraction bars to represent \( \frac{5}{8} \).
  • Remove 2 parts from the bar to represent subtraction.
  • Observe the remaining fraction: \( \frac{3}{8} \).

 

Fractions

 

 

 

Fractons

\( \frac{5}{8}\)

\( \frac{5}{8} - \frac{2}{8} \) = \( \frac{3}{8}\)

 

In this example, the difference is a fraction already in simplest form. 

Example 2: Subtraction with Simplified Difference

Subtract: \( \frac{7}{12} - \frac{3}{12} \).

  • Step 1: Ensure the denominators are the same (12).
  • Step 2: Subtract the numerators: \( 7 - 3 = 4 \).
  • Step 3: Write the fraction: \( \frac{4}{12} \).
  • Step 4: Simplify if possible: \( \frac{4}{12} = \frac{1}{3} \).

In this example, the difference is not in simplest form and has to be simplified. If using a fraction calculator the difference is shown in simplest form.

 

Fractions

 

Example 3: Real-world Application

You have \( \frac{3}{4} \) of a pizza, and you eat \( \frac{1}{4} \). How much pizza is left?

  • Write as \( \frac{3}{4} - \frac{1}{4} = \frac{2}{4} \).
  • Simplify to \( \frac{1}{2} \).
  • Use Media4Math's pizza slice clip art to visually demonstrate this.

 

Before

After

FractionsFractions

 

Example 4: Subtracting Large Fractions

Subtract: \( \frac{13}{20} - \frac{7}{20} \).

  • Step 1: Subtract the numerators: \( 13 - 7 = 6 \).
  • Step 2: Keep the denominator: \( \frac{6}{20} \).
  • Step 3: Simplify:

 \( \frac{6}{20} \) =  \( \frac{2•3}{2•10} \)

=  \( \frac{2}{10} \)

Example 5: Real-world Problem

A recipe calls for \( \frac{5}{6} \) cup of sugar. You only use \( \frac{2}{6} \) cup. How much more do you need to use?

 

Needed

Have

FractionsFractions

\( \frac{5}{6} \)

\( \frac{2}{6} \)

 

  • Write as \( \frac{5}{6} \) - \( \frac{2}{6} \) = \( \frac{3}{6} \).
  • Simplify to \( \frac{1}{2} \).
  • Visualize with a number line showing parts of a whole.

 

Fractions

 

Multimedia Resources

 

 

Review

Steps for Subtracting Fractions with Like Denominators

Follow these steps to subtract fractions with like denominators:

  • Identify the denominators to confirm they are the same.
  • Subtract the numerators while keeping the denominator unchanged.
  • Simplify the resulting fraction by dividing both the numerator and denominator by their greatest common factor (GCF), if possible.
  • Check your solution by visualizing the problem or reworking the calculation.

Example 1: Reviewing Simple Subtraction

Subtract: \( \frac{9}{14} - \frac{5}{14} \).

  • Step 1: Ensure the denominators are the same (14).
  • Step 2: Subtract the numerators: \( 9 - 5 = 4 \).
  • Step 3: Write the fraction: \( \frac{4}{14} \).
  • Step 4: Simplify if necessary: \( \frac{4}{14} = \frac{2}{7} \).

Example 2: Reviewing Subtraction with Visuals

Subtract: \( \frac{7}{9} - \frac{4}{9} \).

  • Use fraction bars to represent \( \frac{7}{9} \).
  • Remove 4 parts from the bar to represent subtraction.
  • Observe the remaining fraction: \( \frac{3}{9} \).
  • Simplify using another fraction bar.

 

FractionsFractionsFractions

 \( \frac{7}{9} \)

 \( \frac{7}{9} - \frac{4}{9} \) =  \( \frac{3}{9} \)

 \( \frac{7}{9} - \frac{4}{9} \) =  \( \frac{1}{3} \)

 

Example 3: Reviewing a Real-world Problem

A juice container has \( \frac{3}{5} \) liters of juice. If you pour out \( \frac{1}{5} \), how much juice is left?

 

Fractions

 

  • Write as \( \frac{3}{5} - \frac{1}{5} = \frac{2}{5} \).
  • Visualize with a fraction model to confirm the solution.

Multimedia Resources

 

 

Quiz

Directions: Subtract the fractions. Simplify your answers if necessary.

  1. \( \frac{5}{8} - \frac{3}{8} \)
  2. \( \frac{7}{10} - \frac{2}{10} \)
  3. \( \frac{12}{15} - \frac{6}{15} \)
  4. \( \frac{9}{16} - \frac{5}{16} \)
  5. \( \frac{8}{12} - \frac{3}{12} \)
  6. \( \frac{13}{18} - \frac{4}{18} \)
  7. \( \frac{6}{9} - \frac{2}{9} \)
  8. \( \frac{10}{20} - \frac{5}{20} \)
  9. \( \frac{15}{25} - \frac{10}{25} \)
  10. \( \frac{14}{21} - \frac{7}{21} \)

Answer Key

1. \( \frac{1}{4} \)

2. \( \frac{1}{2} \)

3. \( \frac{2}{5} \)

4. \( \frac{1}{4} \)

5. \( \frac{5}{12} \)

6. \( \frac{1}{2} \)

7. \( \frac{4}{9} \)

8. \( \frac{1}{4} \)

9. \( \frac{1}{5} \)

10. \( \frac{1}{3} \)