Math lesson plan · 1st grade (Year 2 in England) · 45 minutes
Subtract by thinking of an addition
Addition and subtraction
CCSS 1.OA.B.4England: Y1 Addition and subtractionEngland: Y2 Addition and subtraction
Objective and success criteria
Students will: Subtract by thinking of an addition.
- 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 within 20; Subtract within 20
Leads to: Fact families within 20; Story problems: find the missing change; Find a difference by counting up
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 within 20; Subtract within 20). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Hiro has 5 stickers. A friend gives Hiro 12 more. How many stickers does Hiro have now? → 17Prompt: Do we join the groups or take away?
- There are 5 stickers in a box and 14 on the table. How many stickers are there in all? → 19Prompt: Do we join the groups or take away?
- Ines has 10 balls. A friend gives Ines 7 more. How many balls does Ines have now? → 17Prompt: Do we join the groups or take away?
Hook · 5 min
- Give a real shopping total or a score difference and ask for a quick estimate first.
- Share the objective: Subtract by thinking of an addition. 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: 7 + 7 = 14. Use this to find 14 − 7.
- Step 1: 14 − 7 = 7
- Answer: 7
- 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.
- 6 + 2 = 8. Use this to find 8 − 6. → 2Prompt: 6 and what make 8?
- To work out 9 − 5, think: 5 + __ = 9 → 4Prompt: Count up from 5 to 9.
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.
- To work out 13 − 7, think: 7 + __ = 13 → 6Prompt: Count up from 7 to 13.
- Which addition helps you work out 10 − 6? (6 + 6 = 12 / 4 + 10 = 14 / 10 + 6 = 16 / 6 + 4 = 10) → 6 + 4 = 10Prompt: The helpful addition uses the same three numbers.
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 within 20.
- 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: Fact families within 20; Story problems: find the missing change; Find a difference by counting up.
- 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