Math lesson plan · 2nd grade (Year 3 in England) · 30 minutes
Find the missing number in additions and subtractions to 100
Addition and subtraction
CCSS 2.OA.A.1CCSS 2.NBT.B.5England: Y2 Addition and subtractionEngland: Y3 Addition and subtraction
Objective and success criteria
Students will: Find the missing number in additions and subtractions to 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: Missing numbers and the equal sign; Find a difference by counting up
Leads to: Story problems: work out the starting amount
Materials: Base-ten blocks, Number lines, Hundred square, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Missing numbers and the equal sign; Find a difference by counting up). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- 5 + 2 = 2 + __ → 5Prompt: The equal sign means both sides have the same value.
- True or false? 3 + 8 = 8 + 3 (True / False) → TruePrompt: Work out the value of each side.
- __ + 2 = 14 → 12Prompt: What do you add to 2 to make 14?
Hook · 3 min
- Give a real shopping total or a score difference and ask for a quick estimate first.
- Share the objective: Find the missing number in additions and subtractions to 100. Read the success criteria together.
I do: model it · 7 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: 35 + __ = 78
- Step 1: 78 − 35 = 43
- Step 2: 43
- Answer: 43
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 6 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- 19 + __ = 74 → 55Prompt: Count up from 19 to 74.
- 75 − __ = 10 → 65Prompt: How much was taken away?
You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.
Exit ticket · 3 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- 35 + __ = 75 → 40Prompt: Count up from 35 to 75.
- __ − 21 = 31 → 52Prompt: The missing number is the whole: the number you started with.
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: Missing numbers and the equal sign.
- 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: Story problems: work out the starting amount.
- 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