Math lesson plan · 2nd grade (Year 3 in England) · 60 minutes
Pairs of numbers that make 100
Addition and subtraction
CCSS 2.NBT.B.5England: Y2 Addition and subtractionEngland: Y3 Addition and subtraction
Objective and success criteria
Students will: Pairs of numbers that make 100.
- 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: Make 10 (number bonds); Count to 100 by ones and tens
Leads to: Give change from one dollar or one pound
Materials: Base-ten blocks, Number lines, Hundred square, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 6 min
- Quick retrieval from earlier learning (Make 10 (number bonds); Count to 100 by ones and tens). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Count by tens. What is missing? 50, __, 70, 80, 90 → 60Prompt: Each number is 10 more than the one before.
- Lucia has 10 pencils. 1 are in the box. How many are not in the box? → 9Prompt: The two groups together make 10.
- Count by tens. What is missing? 10, __, 30, 40, 50 → 20Prompt: Each number is 10 more than the one before.
Hook · 6 min
- Give a real shopping total or a score difference and ask for a quick estimate first.
- Share the objective: Pairs of numbers that make 100. 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: 10 + __ = 100
- Step 1: 10 + 90 = 100
- Step 2: 90
- Answer: 90
- 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.
- 40 + __ = 100 → 60Prompt: 4 tens and how many more tens make 10 tens?
- 50 + __ = 100 → 50Prompt: First get to the next ten.
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.
- 10 + __ = 100 → 90Prompt: First get to the next ten.
- Hana says 13 + 97 = 100. What number should go with 13 to make 100? → 87Prompt: Check Hana's answer: does 13 + 97 really make 100?
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: Make 10 (number bonds).
- 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: Give change from one dollar or one pound.
- 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-2.
Free lesson plan from eurekami.com/lesson-plan-builder