Math lesson plan · 6th grade (Year 7 in England) · 60 minutes
Least common multiple of two or three numbers
Number sense
CCSS 6.NS.B.4England: KS3 NumberEngland: GCSE Foundation Number
Objective and success criteria
Students will: Least common multiple of two or three numbers.
- 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 and least common multiple
Leads to: Choose GCF or LCM to solve a problem
Materials: Place value chart, Base-ten blocks or a number line, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 6 min
- Quick retrieval from earlier learning (Greatest common factor and least common multiple). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Find the greatest common factor (highest common factor) of 35 and 56. → 7Prompt: List the factors of each number.
- Find the least common multiple (lowest common multiple) of 7 and 10. → 70Prompt: Count in 10s.
- Kofi buys bread rolls in packs of 12 and veggie sausages in packs of 15. What is the smallest number of rolls Kofi can buy so that there are exactly as many rolls as sausages? → 60Prompt: The number must be a multiple of both pack sizes.
Hook · 6 min
- Show a number in the news or a price tag and ask what each digit is worth.
- Share the objective: Least common multiple of two or three numbers. 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: Find the LCM (lowest common multiple) of 4 and 2.
- Step 1: Multiples of 4: 4
- Step 2: LCM = 4
- Answer: 4
- 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.
- Find the LCM (lowest common multiple) of 8 and 6. → 24Prompt: List multiples of 8.
- 28 = 2² × 7 and 42 = 2 × 3 × 7. Find the LCM of 28 and 42. → 84Prompt: Use every prime that appears in either factorisation.
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.
- 18 = 2 × 3² and 30 = 2 × 3 × 5. Find the LCM of 18 and 30. → 90Prompt: Use every prime that appears in either factorisation.
- Find the LCM (lowest common multiple) of 3 and 5. → 15Prompt: List multiples of 5.
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 and least common multiple.
- 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
- Move on to: Choose GCF or LCM to solve a problem.
- 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