Math lesson plan · 7th grade (Year 8 in England) · 45 minutes
Subtract integers by adding the opposite
Number sense
CCSS 7.NS.A.1.CEngland: KS3 NumberEngland: GCSE Foundation Number
Objective and success criteria
Students will: Subtract integers by adding the opposite.
- 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 integers using sign rules
Leads to: Solve integer problems about temperature, height and money; Add and subtract negative decimals; Add and subtract negative fractions
Materials: Place value chart, Base-ten blocks or a number line, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Add integers using sign rules). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- −15 + (−39) = ? → -54Prompt: Same signs: add the sizes and keep the sign.
- 16 + (−71) = ? → -55Prompt: Different signs: subtract the smaller size from the larger size.
- 18 + 7 + (−3) + (−7) = ? → 15Prompt: Add all the positives together and all the negatives together.
Hook · 5 min
- Show a number in the news or a price tag and ask what each digit is worth.
- Share the objective: Subtract integers by adding the opposite. 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: −3 − (−11) = ?
- Step 1: −3 − (−11) = −3 + 11
- Step 2: = 8
- Answer: 8
- 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.
- 16 − (−13) = ? → 29Prompt: Subtracting a negative is the same as adding a positive.
- −19 − 36 = ? → -55Prompt: Rewrite as −19 + (−36).
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.
- Leo says −2 − (−5) = −7. What is the correct answer? → 3Prompt: Leo treated “− (−5)” as adding −5.
- −13 − 2 = ? → -15Prompt: Rewrite as −13 + (−2).
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: Add integers using sign rules.
- 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: Solve integer problems about temperature, height and money; Add and subtract negative decimals; Add and subtract negative fractions.
- 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-7.
Free lesson plan from eurekami.com/lesson-plan-builder