Adding and Subtracting Fractions

Lesson Overview

Class: 3rd and 4th class (Age 8-10)
Duration: 45 minutes
Class Size: 24 students
Curriculum Alignment: Irish Primary Curriculum - Mathematics
Strand: Number
Strand Unit: Fractions

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Learning Objectives

By the end of this lesson, students will:

• Understand how to add and subtract simple fractions with the same denominator.
• Use concrete materials (fraction strips/circles) to model addition and subtraction of fractions.
• Develop strategies to solve fraction addition and subtraction problems confidently.

Irish Curriculum References:

• Number strand: Develop understanding of fractions as part of a whole (pupils explore fractions and perform simple operations).
• Strand Unit: Fractions (3rd/4th Class) - Pupils add and subtract fractions with the same denominator and represent results concretely and pictorially.
• Strand Unit Goal: Pupils begin to develop fluency in procedures involving fractions and understand their meaning in context.

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Success Criteria

I can:

• Use fraction strips or circles to model adding and subtracting fractions with the same denominator.
• Write addition and subtraction number sentences involving fractions.
• Explain why only the numerators change when adding or subtracting fractions with the same denominator.
• Solve real-life problems involving adding and subtracting simple fractions.

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Materials Needed

• Fraction strips or paper fraction circles for each student or pair
• Whiteboards and markers
• Worksheets with addition and subtraction problems
• Visual fraction number lines (optional)

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Lesson Structure

1. Introduction (5 minutes)

• Brief review of previously learned fraction concepts (e.g., what a fraction is, same denominator meaning).
• Recap key vocabulary: numerator, denominator, fraction, adding, subtracting.
• Set the learning intention and success criteria explicitly on the board.
• Engage with quick Q&A: “What happens to the denominators when adding fractions with the same denominators?”

2. Modelling & Guided Practice (10 minutes)

• Model addition and subtraction using fraction strips or circles:
  • Example: 3/8 + 2/8: Physically combine 3 parts and 2 parts out of 8.
  • Emphasise that denominators stay the same, numerators add or subtract.
• Demonstrate on a whiteboard: Write 3/8 + 2/8 = 5/8 and explain each step.
• Repeat for subtraction: 5/8 - 2/8 = 3/8.
• Invite students to model a similar problem on their fraction strips/circles with a partner.

3. Paired Hands-on Activity (15 minutes)

• Hand out fraction strips/circles and worksheets.
• Students work in pairs to solve a set of 6 problems—3 addition, 3 subtraction—using the manipulatives to find answers first, then write number sentences to match.
• Circulate to provide support and challenge where necessary.

4. Differentiation

• Support for learners who find fractions challenging:
  • Use only fractions with denominators 2, 3, or 4 for easier visualisation.
  • Provide extra guided modelling and allow use of number lines alongside fraction strips.
  • Pair with a peer mentor for support.
• Support for learners with fine motor difficulties:
  • Use larger, pre-cut fraction circles/strips to facilitate handling.

5. Extension Activities for Advanced Learners (10 minutes)

• Challenge these students to solve problems involving adding and subtracting three or more fractions with the same denominators.
• Introduce word problems requiring reasoning, for example: "Emily ate 2/8 of a cake, and Mia ate 4/8 of the same cake. How much cake was eaten in total?"
• Encourage them to explain their thinking in complete sentences, both orally and written.
• Suggest exploring equivalent fractions where denominators are the same (for early preparation).

6. Formative Assessment & Review (5 minutes)

• Quick individual whiteboard quiz: Students write answers to teacher-posed addition or subtraction fraction problems with the same denominator (e.g., 4/9 + 3/9).
• Use thumbs-up/thumbs-down or traffic light cards to self-assess understanding.
• Teacher notes common misconceptions for future lessons, especially around denominator invariance.
• End with a reflective question: “Why do you think the denominator doesn’t change when adding or subtracting these fractions?”

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Reflection & Planning Notes for Teacher

• Monitor which students grasp the concept confidently and who need further concrete experience.
• Emphasise language and encourage students to verbalise steps as they work.
• Prepare follow-up tasks for students who mastered this quickly, including mixed denominator operations (next step).
• Consider sending home fraction strips copies or links to online interactive fraction tools for reinforcement.

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This lesson plan provides a balance of concrete, pictorial, and abstract learning modes firmly rooted in the Irish Curriculum number and fractions strand, ensuring all pupils build a solid, meaningful understanding of fraction addition and subtraction.