Math lesson plan · 3rd grade (Year 4 in England) · 45 minutes
Subtract three-digit numbers with exchanging
Addition and subtraction
CCSS 3.NBT.A.2England: Y3 Addition and subtraction
Objective and success criteria
Students will: Subtract three-digit numbers with exchanging.
- 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: Add and subtract within 1000; Subtract two-digit numbers with regrouping
Leads to: Subtract four-digit numbers in columns; Find missing digits in column sums; Check answers with the inverse operation
Materials: Base-ten blocks, Number lines, Hundred square, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Add and subtract within 1000; Subtract two-digit numbers with regrouping). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- What is 10 less than 123? → 113Prompt: Which digit changes when you subtract 10?
- What is 10 more than 324? → 334Prompt: Which digit changes when you add 10?
- What is 10 less than 362? → 352Prompt: Which digit changes when you subtract 10?
Hook · 5 min
- Give a real shopping total or a score difference and ask for a quick estimate first.
- Share the objective: Subtract three-digit numbers with exchanging. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: 313 − 175 = ?
- Step 1: ones: exchange, 13 − 5 = 8
- Step 2: tens: exchange, 10 − 7 = 3
- Step 3: hundreds: 2 − 1 = 1
- Step 4: 313 − 175 = 138
- Answer: 138
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- 422 − 253 = ? → 169Prompt: Start with the ones.
- 605 − 586 = ? → 19Prompt: There is a 0 in the tens. Exchange from the hundreds first.
You do: independent practice · 10 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 · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- A book has 937 pages. Mei has read 262 pages. How many pages are left? → 675Prompt: 'How many are left' means subtract.
- 577 − 471 = ? → 106Prompt: Start with the ones.
Watch out for
- Subtracting the smaller digit from the bigger one in every column (52 − 17 = 45).
- Forgetting to add the regrouped (carried) ten.
Support and stretch
Support
- Review first: Add and subtract within 1000.
- Use concrete materials: base-ten blocks.
- 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: Subtract four-digit numbers in columns; Find missing digits in column sums; Check answers with the inverse operation.
- 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