Math lesson plan · 4th grade (Year 5 in England) · 45 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 · 5 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 563 + 596 by rounding each number to the nearest hundred first. → 1200Prompt: Round 563 to the nearest 100.
- Round 489 303 to the nearest 10 000. → 490000Prompt: Which two multiples of 10 000 is it between?
- Hiro wants to estimate 539 − 182. Which is the best estimate? (400 / 200 / 300 / 30) → 300Prompt: Round both numbers to the nearest hundred.
Hook · 5 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 · 10 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 · 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.
- Estimate 6058 + 7318 by rounding each number to the nearest thousand. → 13000Prompt: Round each number first.
- Fatima added 59 629 + 11 287 and got 80 916. Round to the nearest ten thousand to estimate. Is Fatima's answer reasonable? (yes / no) → noPrompt: Round both numbers to the nearest 10 000.
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.
- Estimate 8891 − 6692 by rounding each number to the nearest thousand. → 2000Prompt: Round each number first.
- Yuki added 31 277 + 15 162 and got 56 439. Round to the nearest ten thousand to estimate. Is Yuki'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