Math lesson plan · 3rd grade (Year 4 in England) · 60 minutes
Add and subtract fractions with the same denominator within one whole
Fractions
CCSS 4.NF.B.3.AEngland: Y3 Fractions
Objective and success criteria
Students will: Add and subtract fractions with the same denominator within one whole.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Understand fractions a/b
Leads to: the next skill in this area.
Materials: Fraction strips or a fraction wall, Paper strips to fold, Number lines, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 6 min
- Quick retrieval from earlier learning (Understand fractions a/b). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
Hook · 6 min
- Cut a pizza or a strip of paper unevenly and ask whether the pieces are really halves or quarters.
- Share the objective: Add and subtract fractions with the same denominator within one whole. Read the success criteria together.
I do: model it · 12 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Grace says 2/10 + 3/10 = 5/20. Spot the mistake. What is the right answer?
- Step 1: Grace added the denominators too.
- Step 2: 5/10
- Answer: 5/10
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 12 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Leo says 4/8 + 1/8 = 5/16. Spot the mistake. What is the right answer? → 5/8Prompt: When you add parts of the same size, does the size of the parts change?
- Elena says 3/5 + 1/5 = 4/10. Spot the mistake. What is the right answer? → 4/5Prompt: When you add parts of the same size, does the size of the parts change?
You do: independent practice · 17 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 7 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Ana says 3/10 + 2/10 = 5/20. Spot the mistake. What is the right answer? → 5/10Prompt: When you add parts of the same size, does the size of the parts change?
- Hana says 6/10 + 1/10 = 7/20. Spot the mistake. What is the right answer? → 7/10Prompt: When you add parts of the same size, does the size of the parts change?
Watch out for
- Thinking a bigger denominator means a bigger fraction (1/8 > 1/4).
- Adding the denominators when adding fractions (1/2 + 1/3 = 2/5).
Support and stretch
Support
- Review first: Understand fractions a/b.
- Use concrete materials: fraction strips or a fraction wall.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-3.
Free lesson plan from eurekami.com/lesson-plan-builder