Math lesson plan · 6th grade (Year 7 in England) · 30 minutes
Rewrite a sum by taking out the GCF
Number sense
CCSS 6.NS.B.4England: KS3 NumberEngland: KS3 Algebra
Objective and success criteria
Students will: Rewrite a sum by taking out the GCF.
- 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: Greatest common factor of two or three numbers
Leads to: the next skill in this area.
Materials: Place value chart, Base-ten blocks or a number line, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Greatest common factor of two or three numbers). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Find the GCF (highest common factor) of 8 and 10. → 2Prompt: List the factors of the smaller number.
- 84 = 2² × 3 × 7 and 126 = 2 × 3² × 7. Use these to find the GCF of 84 and 126. → 42Prompt: Take each prime that appears in BOTH factorisations.
- Find the GCF of 6, 21, 9. → 3Prompt: Find a number that divides all three.
Hook · 3 min
- Show a number in the news or a price tag and ask what each digit is worth.
- Share the objective: Rewrite a sum by taking out the GCF. Read the success criteria together.
I do: model it · 7 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: 36 + 42 = □ × (6 + 7). What number goes in the box?
- Step 1: 6 × 6 = 36, 6 × 7 = 42
- Step 2: The box is 6.
- Answer: 6
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 6 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- 70 + 50 = □ × (7 + 5). What number goes in the box? → 10Prompt: The box multiplies each number in the brackets.
- Complete using the GCF: 45 + 105 = 15(3 + □) → 7Prompt: 15(3 + □) means 15 × 3 + 15 × □.
You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.
Exit ticket · 3 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Write 16 + 24 as the GCF times a sum of two whole numbers with no common factor, like 4(2 + 3). → 8(2 + 3)Prompt: Find the GCF of 16 and 24.
- 16 + 24 = □ × (2 + 3). What number goes in the box? → 8Prompt: The box multiplies each number in the brackets.
Watch out for
- Reading 1,045 as one thousand four hundred five: point to each place and say its value.
- Thinking a longer number is always bigger, even with decimals (0.45 vs 0.5).
Support and stretch
Support
- Review first: Greatest common factor of two or three numbers.
- Use concrete materials: place value chart.
- 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-6.
Free lesson plan from eurekami.com/lesson-plan-builder