Math lesson plan · 3rd grade (Year 4 in England) · 30 minutes
Rounding puzzles: which numbers round to …?
Number sense
CCSS 3.NBT.A.1England: Y3 Number and place valueEngland: Y4 Number and place value
Objective and success criteria
Students will: Rounding puzzles: which numbers round to …?.
- 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: Round to the nearest 10 or 100
Leads to: Rounding: greatest and least possible numbers
Materials: Place value chart, Base-ten blocks or a number line, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Round to the nearest 10 or 100). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Which number rounds to 20 when rounded to the nearest 10? (16 / 31 / 25) → 16Prompt: Numbers from 15 up to 24 round to 20.
- Which number rounds to 90 when rounded to the nearest 10? (95 / 84 / 85) → 85Prompt: Numbers from 85 up to 94 round to 90.
- Which number rounds to 70 when rounded to the nearest 10? (81 / 80 / 66) → 66Prompt: Numbers from 65 up to 74 round to 70.
Hook · 3 min
- Show a number in the news or a price tag and ask what each digit is worth.
- Share the objective: Rounding puzzles: which numbers round to …?. 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: What is the smallest whole number that rounds to 410 when rounded to the nearest 10?
- Step 1: 405 is halfway and rounds up to 410.
- Step 2: 405
- Answer: 405
- 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.
- What is the smallest whole number that rounds to 300 when rounded to the nearest 100? → 250Prompt: Halfway between two multiples of 100 rounds up.
- Which number rounds to 500 when rounded to the nearest hundred? (585 / 421 / 558 / 492) → 492Prompt: Numbers from 450 up to 549 round to 500.
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.
- Which number rounds to 900 when rounded to the nearest hundred? (995 / 878 / 963 / 834) → 878Prompt: Numbers from 850 up to 949 round to 900.
- What is the greatest whole number that rounds to 400 when rounded to the nearest 100? → 449Prompt: Halfway between two multiples of 100 rounds up.
Watch out for
- Reading 1,045 as one thousand four hundred five: point to each place and say its value.
- Thinking a longer number is always bigger, even with decimals (0.45 vs 0.5).
Support and stretch
Support
- Review first: Round to the nearest 10 or 100.
- Use concrete materials: place value chart.
- 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: Rounding: greatest and least possible numbers.
- 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-3.
Free lesson plan from eurekami.com/lesson-plan-builder