Year 2 - Maths
Use efficient methods to solve subtraction equations
Addition and subtraction of two 2-digit numbers
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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 apply their knowledge of known facts and understanding of place value to add and subtract with 2-digit numbers both within and across the tens boundary.
Lesson Summary
You will learn to use efficient methods to solve subtraction equations.
Key Notes
- Consecutive numbers always have a difference of 1
- If the whole and the known part in a subtraction equation are consecutive numbers, the missing part will always be 1
- If the known part in a subtraction equation is 1, the whole and the missing part will be consecutive numbers
- When the ones digits in the whole and the known part are the same, the missing part will be a multiple of 10
Vocabulary To Learn
- Consecutive: Numbers which follow each other in order, without gaps.
- Difference: The result of subtracting one number from another.
- Whole: All of something; complete.
- Part: A piece or section of a whole.
Common Mistakes To Avoid
- When writing equations with consecutive numbers, children may write in the order they are counted , e.g. 56-57 = forwards
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Consecutive numbers always have a difference of 1. If the whole and the known part in a subtraction equation are consecutive numbers, the missing part will always be 1.
2. Use this key word in a maths sentence and explain it clearly. 'Consecutive'
Numbers which follow each other in order, without gaps. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: When writing equations with consecutive numbers, children may write in the order they are counted , e.g. 56-57 = forwards. Correction: Give missing number equations and represent them on part-part-whole models and bar models to consolidate understanding of which numbers in the equation represent the whole and the parts.
More Lessons In This Unit
- Add 2-digit numbers when crossing the tens boundary Study Guide
- Add two-digit numbers without crossing the tens boundary Study Guide
- Combine tens and ones within equations Study Guide
- Create addition and subtraction problems Study Guide
- Explain different strategies used to subtract Study Guide
- Find the missing addend when adding two-digit numbers Study Guide
- Find the missing part when subtracting two-digit numbers Study Guide
- Solve equations involving the subtraction of two-digit numbers Study Guide
- Solve problems involving addition and subtraction Study Guide
- Solve problems involving subtraction of two-digit numbers Study Guide
- Solve problems involving subtraction when bridging 10 Study Guide
- Solve problems involving the addition of two-digit numbers Study Guide
- Subtract two-digit numbers crossing the tens boundary Study Guide
- Use efficient addition strategies to calculate Study Guide
Browse all guides in the Year 2 Maths guide library.