Math lesson plan · 1st grade (Year 2 in England) · 45 minutes
Add a one-digit number to a two-digit number (no new ten)
Addition and subtraction
CCSS 1.NBT.C.4England: Y1 Addition and subtractionEngland: Y2 Addition and subtraction
Objective and success criteria
Students will: Add a one-digit number to a two-digit number (no new ten).
- 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: Tens and ones; Add within 10
Leads to: Add a one-digit number to a two-digit number (making a new ten); Add two-digit numbers without 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 (Tens and ones; Add within 10). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- How many tens are in 49? → 4Prompt: In a two-digit number, the left digit tells the tens and the right digit tells the ones.
- 15 = 1 tens and how many ones? → 5Prompt: In a two-digit number, the left digit tells the tens and the right digit tells the ones.
- 78 = 7 tens and how many ones? → 8Prompt: In a two-digit number, the left digit tells the tens and the right digit tells the ones.
Hook · 5 min
- Give a real shopping total or a score difference and ask for a quick estimate first.
- Share the objective: Add a one-digit number to a two-digit number (no new ten). 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: Use the fact 1 + 7 = 8 to work out 71 + 7.
- Step 1: 70 + 8 = 78
- Step 2: 78
- Answer: 78
- 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.
- Use the fact 3 + 3 = 6 to work out 63 + 3. → 66Prompt: 63 is 60 + 3.
- Kofi worked out 91 + 2 = 111. What mistake did Kofi make? (Added 2 to the tens instead of the ones / Forgot to add the tens / No mistake: it is right) → Added 2 to the tens instead of the onesPrompt: What is the right answer to 91 + 2?
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.
- Felix worked out 70 + 5 = 120. What mistake did Felix make? (Added 5 to the tens instead of the ones / Forgot to add the tens / No mistake: it is right) → Added 5 to the tens instead of the onesPrompt: What is the right answer to 70 + 5?
- Use the fact 1 + 2 = 3 to work out 21 + 2. → 23Prompt: 21 is 20 + 1.
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: Tens and ones.
- 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: Add a one-digit number to a two-digit number (making a new ten); Add two-digit numbers without 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