Math lesson plan · 4th grade (Year 5 in England) · 30 minutes
Use rounding to check if an answer is reasonable
Addition and subtraction
CCSS 4.OA.A.3CCSS 4.NBT.A.3England: Y5 Addition and subtraction
Objective and success criteria
Students will: Use rounding to check if an answer is reasonable.
- 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: Estimate sums and differences; Round multi-digit numbers
Leads to: the next skill in this area.
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 (Estimate sums and differences; Round multi-digit numbers). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Estimate 631 + 578 by rounding each number to the nearest hundred first. → 1200Prompt: Round 631 to the nearest 100.
- Round 95 267 to the nearest 1000. → 95000Prompt: Which two multiples of 1000 is it between?
- Ethan wants to estimate 598 + 415. Which is the best estimate? (100 / 1000 / 900 / 1100) → 1000Prompt: Round both numbers to the nearest hundred.
Hook · 3 min
- Give a real shopping total or a score difference and ask for a quick estimate first.
- Share the objective: Use rounding to check if an answer is reasonable. 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: Estimate 7242 − 3757 by rounding each number to the nearest thousand.
- Step 1: 7242 ≈ 7000, 3757 ≈ 4000
- Step 2: 7000 − 4000 = 3000
- Answer: 3000
- 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.
- Estimate 3055 − 2218 by rounding each number to the nearest thousand. → 1000Prompt: Round each number first.
- Amara added 36 913 + 14 216 and got 61 129. Round to the nearest ten thousand to estimate. Is Amara's answer reasonable? (yes / no) → noPrompt: Round both numbers to the nearest 10 000.
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.
- Estimate 6491 − 5724 by rounding each number to the nearest thousand. → 0Prompt: Round each number first.
- Zara added 28 600 + 22 776 and got 41 376. Round to the nearest ten thousand to estimate. Is Zara's answer reasonable? (yes / no) → noPrompt: Round both numbers to the nearest 10 000.
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: Estimate sums and differences.
- 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
- 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-4.
Free lesson plan from eurekami.com/lesson-plan-builder