Year 2 - Maths
Add and subtract 10 to and from a 2-digit number.
Adding and subtracting ones and tens to and from 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 will add and subtract 1s and 10s from 2 digit numbers. They will use number facts to add/subtract a single-digit number to/from a 2-digit number. They will use a part-part-whole model to represent addition and subtraction.
Lesson Summary
You will learn to add and subtract 10 to and from a two-digit number.
Key Notes
- When adding or subtracting 10, the ones digits does not change.
- When adding 10, the tens digit increases by one; when subtracting 10, the tens digit decreases by one.
- When numbers have the same ones digit and the tens digit has a difference of one, they will have a difference of 10
- Understanding the patterns when we add and subtract 10 can help us solve equations efficiently.
Vocabulary To Learn
- Efficiently: Not wasting time or effort. An efficient strategy is one we can carry out easily.
Common Mistakes To Avoid
- Children may focus on the ones digit rather than the tens digits. They may calculate inefficiently by counting on/back in ones rather than using the pattern in the tens digits.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When adding or subtracting 10, the ones digits does not change. When adding 10, the tens digit increases by one; when subtracting 10, the tens digit decreases by one.
2. Use this key word in a maths sentence and explain it clearly. 'Efficiently'
Not wasting time or effort. An efficient strategy is one we can carry out easily. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Children may focus on the ones digit rather than the tens digits. They may calculate inefficiently by counting on/back in ones rather than using the pattern in the tens digits. Correction: Use Base 10 equipment alongside one hundred squares to support with understanding the structure of adding or subtracting ten and difference. Encourage children to notice what changes and what stays the same.
More Lessons In This Unit
- Add and subtract 1 to and from a 2-digit number crossing the tens boundary Study Guide
- Add and subtract one to or from a two-digit number within a decade Study Guide
- Add by bridging a multiple of ten Study Guide
- Add multiples of 10 to 2-digit numbers. Study Guide
- Find 10 more or less than a 2-digit number. Study Guide
- Partition 2-digit numbers in different ways Study Guide
- Subtract by bridging a multiple of ten Study Guide
- Subtract multiples of ten from 2-digit numbers Study Guide
- Use bridging to solve addition and subtraction problems Study Guide
- Use efficient strategies to solve problems Study Guide
- Use number bonds to 10 to add/subtract one-digit and two-digit numbers Study Guide
- Use number facts to add or subtract a one-digit number and a two-digit number. Study Guide
- Use number facts to solve addition and subtraction problems. Study Guide
- Use number facts to solve problems in measures and data contexts Study Guide
Browse all guides in the Year 2 Maths guide library.