Mathematics · Primary 4

Active learning ideas

Adding and Subtracting Like Fractions

Active learning works for adding and subtracting like fractions because students need to see numerators and denominators separately, not as whole numbers. Handling physical or visual fraction pieces lets children test why denominators stay the same while numerators combine or separate.

• MOE Syllabus Outcomes
• MOE: Numbers and their operations - S1

• 25–40 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Problem-Based Learning
• 30 min · Pairs

Fraction Bar Addition: Visual Matching

Provide pre-cut fraction bars for halves, thirds, and quarters. In pairs, students select bars with the same denominator, lay them side by side to add lengths, and record the sum as a single fraction. They then subtract by removing bars and verify with drawings.

How do you add two fractions that have the same denominator?

Facilitation Tip

During Fraction Bar Addition, ask pairs to build the same fraction twice using different fraction bars to prove the denominator stays fixed.

What to look for

Present students with three problems on a worksheet: 1/5 + 3/5, 7/10 - 2/10, and a simple word problem like 'Sarah ate 2/8 of a pie and John ate 3/8. What fraction of the pie did they eat altogether?'. Review answers as a class.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 02

• Problem-Based Learning
• 35 min · Small Groups

Pizza Sharing Relay: Small Group Challenge

Divide paper pizzas into like fractions. Groups take turns adding or subtracting slices as per word problem cards, passing to the next member after simplifying. The group checks the final fraction against the whole pizza.

What do you need to do before you can add fractions that have different denominators?

Facilitation Tip

In Pizza Sharing Relay, assign each group a different pizza size so they must adjust their fractions to match before adding or subtracting.

What to look for

Give each student a card with a problem such as 'Calculate 5/9 + 2/9'. Ask them to write the answer and one sentence explaining how they got it. Collect these as students leave.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 03

• Problem-Based Learning
• 40 min · Whole Class

Fraction Line Plot: Whole Class Data

Students measure and record lengths like 1/4 m ribbons on a class number line. As a group, add total lengths of like fractions, then subtract to find net usage. Discuss patterns observed.

Can you solve a word problem involving adding or subtracting fractions and check that your answer makes sense?

Facilitation Tip

For the Fraction Line Plot, have students mark their answers on a large number line to see how fractions combine or separate visually.

What to look for

Pose the question: 'Imagine you have 7/12 of a chocolate bar and you give away 3/12. How much chocolate do you have left? Explain your steps to a partner.' Have a few students share their explanations with the class.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 04

• Problem-Based Learning
• 25 min · Individual

Error Hunt Cards: Individual Practice

Distribute cards with addition/subtraction problems, some correct and some with errors. Students identify mistakes, explain fixes, and create their own correct examples for sharing.

How do you add two fractions that have the same denominator?

Facilitation Tip

When using Error Hunt Cards, encourage students to explain their corrections aloud so peers hear the reasoning behind each step.

What to look for

Present students with three problems on a worksheet: 1/5 + 3/5, 7/10 - 2/10, and a simple word problem like 'Sarah ate 2/8 of a pie and John ate 3/8. What fraction of the pie did they eat altogether?'. Review answers as a class.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

A few notes on teaching this unit

Teachers should start with real objects students can touch and move, like paper fraction tiles or fraction circles, before moving to drawings or symbols. Avoid rushing to the algorithm; let students discover the rule that denominators stay the same on their own. Research shows that students who manipulate concrete models before abstract symbols retain the concept longer.

Students will confidently add or subtract fractions with the same denominator and simplify when necessary. They will explain their steps using visual models or words, showing they understand the process rather than just following a rule.

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Watch Out for These Misconceptions

• During Fraction Bar Addition, watch for students who add both numerators and denominators.

  Have students lay two fraction bars of the same denominator side by side and count the total shaded parts to see why only numerators combine.

• During Pizza Sharing Relay, watch for students who leave sums or differences in improper fractions without simplifying.

  Prompt groups to trade four 1/4 pieces for a whole circle when they reach 4/4, making simplification visible and automatic.

• During Fraction Line Plot, watch for students who subtract numerators without checking if the top fraction is larger.

  Ask students to shade the whole fraction on a circle model first, then cross out the part being subtracted to see if regrouping is needed.

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Methods used in this brief

• Problem-Based Learning