Year 3 - Maths
Composition of 100 in 50s, 25s and 20s
Securing place value to 100 and applying to addition and subtraction
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will use known facts to find multiples of ten that compose 100 and use known facts to find complements to 100. They will add and subtract multiples of ten, bridging 100.
Lesson Summary
You will learn to compose 100 in 50s, 25s and 20s.
Key Notes
- 100 can be divided into equal parts
- There are two 50s in 100
- There are four 25s in 100
- There are five 20s in 100
Vocabulary To Learn
- Compose: You can compose larger numbers from smaller numbers.
- Decompose: You can decompose whole numbers into smaller numbers.
Common Mistakes To Avoid
- Pupils may believe only multiples of 10 can compose 100 and therefore do not see four groups of 25.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
100 can be divided into equal parts. There are two 50s in 100.
2. Use this key word in a maths sentence and explain it clearly. 'Compose'
You can compose larger numbers from smaller numbers. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils may believe only multiples of 10 can compose 100 and therefore do not see four groups of 25. Correction: Focus on practical representations e.g. bead strings and base 10 blocks where 100 can be composed and decomposed.
More Lessons In This Unit
- Bridge 100 by adding in multiples of 10 Study Guide
- Bridge 100 by subtracting in multiples of 10 Study Guide
- Composition of 100 in 10s and 1s Study Guide
- Multiples of 10 that total 100 Study Guide
- Represent 3-digit multiples of 10 in different ways Study Guide
- Solve problems using knowledge of addition and subtraction of multiples of 10 Study Guide
- Use known facts to find complements to 100 efficiently Study Guide
- Use known facts to find pairs of numbers that total 100 Study Guide
- Use place value knowledge to write addition and subtraction equations Study Guide
Browse all guides in the Year 3 Maths guide library.