Math lesson plan · 1st grade (Year 2 in England) · 45 minutes
Subtract within 20
Addition and subtraction
CCSS 1.OA.C.6CCSS 1.OA.A.1England: Y1 Addition and subtraction
Objective and success criteria
Students will: Subtract within 20.
- 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: Subtract within 10; Add within 20
Leads to: Missing numbers and the equal sign; Word problems within 20; Subtract two-digit numbers with regrouping
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 (Subtract within 10; Add within 20). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- There were 4 marbles. Then 3 were used. How many are left? → 1Prompt: Is something being taken away, or are we comparing?
- Luis has 8 beads. Yuki has 3. How many more beads does Luis have than Yuki? → 5Prompt: Is something being taken away, or are we comparing?
- Maya had 10 apples and gave away 2. How many apples are left? → 8Prompt: Is something being taken away, or are we comparing?
Hook · 5 min
- Give a real shopping total or a score difference and ask for a quick estimate first.
- Share the objective: Subtract within 20. 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: Amara has 19 stars. Jamal has 4. How many more stars does Amara have than Jamal?
- Step 1: 19 − 4 = 15
- Answer: 15
- 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.
- Omar has 12 cards. Maya has 2. How many more cards does Omar have than Maya? → 10Prompt: Are we taking away or finding a difference? Both are subtraction.
- If 8 + 6 = 14, what is 14 − 8? → 6Prompt: Addition and subtraction are a fact family.
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.
- If 4 + 11 = 15, what is 15 − 4? → 11Prompt: Addition and subtraction are a fact family.
- Fatima has 13 crayons. Liam has 4. How many more crayons does Fatima have than Liam? → 9Prompt: Are we taking away or finding a difference? Both are subtraction.
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: Subtract within 10.
- 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: Missing numbers and the equal sign; Word problems within 20; Subtract two-digit numbers with regrouping.
- 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-1.
Free lesson plan from eurekami.com/lesson-plan-builder