Year 2 - Maths
Add two-digit numbers without crossing the tens boundary
Addition and subtraction of two 2-digit numbers
Study Hub
Study Guides
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 add two-digit numbers without crossing the tens boundary.
Key Notes
- Two-digit numbers can be added by using Base 10 equipment to combine the tens and the ones.
- Partitioning two-digit numbers can help when adding them.
- Either the tens or the ones can be added first, the sum will remain the same.
- Considering the number of tens when adding two-digit numbers can help estimate the sum.
Vocabulary To Learn
- Partition: To split a whole up into parts.
Common Mistakes To Avoid
- Children may transpose digits in the numbers, so add tens as ones and vice versa. They may also use inefficient counting strategies to count on in tens, then ones.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Two-digit numbers can be added by using Base 10 equipment to combine the tens and the ones. Partitioning two-digit numbers can help when adding them.
2. Use this key word in a maths sentence and explain it clearly. 'Partition'
To split a whole up into parts. 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 transpose digits in the numbers, so add tens as ones and vice versa. They may also use inefficient counting strategies to count on in tens, then ones. Correction: Ensure that the numbers are partitioned into tens and ones, so their place value is clear and the link to known facts can be easily seen. Refer back to known facts using the stem sentence 'I know that..., so I know that ...'.
More Lessons In This Unit
- Add 2-digit numbers when 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
- Use efficient methods to solve subtraction equations Study Guide
Browse all guides in the Year 2 Maths guide library.