Rounding to 100

National Curriculum Links

• Mathematics - Number - Number and place value:
  • Year 4: "Recognise the place value of each digit in a four-digit number (thousands, hundreds, tens, and ones). Round any number to the nearest 10, 100 or 1000."

This lesson directly addresses the objective: "Round any number to the nearest 100."

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Lesson Overview

• Duration: 60 minutes
• Class size: 30 students
• Topic: Rounding numbers to the nearest 100
• Age Group: Year 4 (ages 8-9)

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Learning Objectives

By the end of this lesson, pupils will be able to:

• Understand and explain the concept of rounding to the nearest 100.
• Accurately round 3- and 4-digit numbers to the nearest 100.
• Justify their rounding decisions using place value knowledge and rounding rules.

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Success Criteria

• I can identify the hundreds digit in a number.
• I can look at the tens digit to decide whether to round up or down.
• I can round numbers like 374 and 845 to the nearest 100 correctly.
• I can explain my rounding choice clearly, using place value language.
• I can check my answers by comparing the rounded number with the original.

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Resources

• Whiteboard and markers
• Place value charts printed for tables/shared
• Sets of number cards (3- and 4-digit numbers)
• Rounding place value mats
• Mini-whiteboards for individual responses
• Interactive rounding game (optional)

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Lesson Structure

1. Introduction and Engagement (10 minutes)

• Start with a quick number sense recall: Write a random 3-digit number (e.g., 376) on the board.
• Ask:
  • “What is the place value of each digit here?” (Check understanding of hundreds, tens, ones.)
  • “If you had to round this number to the nearest 10, what would you do?” (Recap Year 3 learning.)
• Introduce the concept of rounding to the nearest 100 with a relatable example:
  “Imagine you are organising books into shelves. Each shelf holds 100 books. If you have 376 books, how many shelves will you need?”
• Display a number line marked in 100s (e.g., 300 - 400) and show where 376 sits.
• Engage with the class by asking:
  • “Do we round 376 up to 400 or down to 300? Why?”
• Introduce success criteria visually.

AFL Checkpoint

• Whole-class discussion, asking students to explain their reasoning verbally.
• Use mini-whiteboards: Write the rounded number to nearest 100 for 3-4 examples and hold up answers.

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2. Modelling (15 minutes)

• Model step-by-step the rounding of numbers to the nearest 100 on the board:
  Example 1: 452
  • Point out the hundreds digit (4), tens digit (5), ones digit (2).
  • Explain the rounding rule (tens digit less than 5, round down, otherwise round up).
  • Show number line: 400 < 452 < 500 and 452 is closer to 500 than 400. So round to 500.
• Repeat with different numbers, including tricky ones like 350 (exact midpoint).
• Write aloud the thinking process using key vocabulary:
  “The tens digit is 5, so we round up the hundreds digit by one.”

AFL Checkpoint

• Ask targeted questions:
  • “Why do we round up when the tens digit is 5 or greater?” (Understanding)
  • “Can you show me a number where we round down?” (Application)
  • Use mini whiteboards for students to write new examples.

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3. Guided Practice (15 minutes)

• Give pairs number cards (e.g. 374, 845, 299, 620) and rounding mats with place values.
• Pupils discuss and round each number to the nearest 100; write answers and explain reasoning aloud to partner.
• Circulate and probe deeper by asking:
  • “What digit are you looking at to make your decision?”
  • “How does the position of the tens digit affect your answer?”
  • “Can you justify why your rounded number is the closest 100 to the original number?”

AFL Checkpoint

• Observe discussions and collect examples of student explanations.
• Support any student misconceptions immediately (see misconceptions below).

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4. Independent Practice (15 minutes)

• Provide worksheet with 10 questions of varied difficulty:
  • Round 3-digit and 4-digit numbers to the nearest 100.
  • Include borderline cases like 350, 2500, 4450.
• Include two reasoning questions requiring explanation:
  1. Explain why you rounded 374 to 400 and not 300.
  2. If a number ends in 50, which 100 will it be rounded to and why?
• Encourage full sentences and place value vocabulary.

AFL Checkpoint

• Collect completed work and review explanations for depth of understanding.

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5. Plenary (5 minutes)

• Recap key concepts with a quick quiz game (e.g., hands up or mini-whiteboard rapid fire).
• Higher-order questioning:
  • “How would you explain rounding to the nearest 100 to a younger student?” (Synthesise)
  • “Is it possible to round a number to two different hundreds at the same time? Why or why not?” (Evaluate)
• Display success criteria and ask pupils to self-assess if they've met each point.

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Common Misconceptions

• Rounding at 50: Pupils often think 50 rounds down instead of up to the next hundred. Clarify the rule: 5 or more rounds up.
• Confusing which digit to focus on: Some focus on ones instead of tens for rounding to 100. Emphasize the importance of the tens digit when rounding to nearest 100.
• Rounding 4-digit numbers as if they were 3-digit: Mistaking thousands digit or not recognising place values correctly.
• Belief that rounding changes the number randomly: Pupils sometimes think rounding is just guessing. Encourage use of number lines and reasoning.

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Targeted Questions (Bloom’s Taxonomy Applied)

Cognitive Level	Question Examples
Remembering	What digit do you look at when rounding to the nearest 100?
Understanding	Why do we round up when the tens digit is 5 or more?
Applying	Round 434 to the nearest 100.
Analysing	Compare the numbers 349 and 351 and explain why they round differently.
Evaluating	Is 450 rounded to 400 correct? Why or why not?
Creating	Create a word problem involving rounding to the nearest 100.

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Additional Extension Ideas (If Time Allows)

• Use an interactive place value chart or digital rounding games on tablets for peer challenge.
• Ask pupils to create their own rounding questions and swap with a partner to solve and justify answers.

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This lesson plan integrates strong formative assessment through questioning and AFL checkpoints, addresses common misconceptions explicitly, and encourages deeper reasoning using Bloom’s taxonomy. It aligns precisely with the Year 4 National Curriculum expectations while engaging learners with hands-on, visual, and collaborative activities.