Year 2 - Maths
Add and subtract one to or from a two-digit number within a decade
Adding and subtracting ones and tens to and from 2-digit numbers
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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 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 1 to and from a 2-digit number within a decade.
Key Notes
- Finding one more is the same as adding 1. Finding one less is the same as subtracting 1
- Numbers that are one more or one less than each other have a difference of one.
Vocabulary To Learn
- One more: The number that is one more than another is the result of adding 1 to that number
- One less: The number that is one less than another is the result of subtracting 1 from that number
- Difference: The result of subtracting one number from another. How much one number differs from another.
Common Mistakes To Avoid
- The language of one more or one less than can confuse children, so 55 is one more than ? may be interpreted as 55 plus 1
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Finding one more is the same as adding 1. Finding one less is the same as subtracting 1. Numbers that are one more or one less than each other have a difference of one.
2. Use this key word in a maths sentence and explain it clearly. 'One more'
The number that is one more than another is the result of adding 1 to that number. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: The language of one more or one less than can confuse children, so 55 is one more than ? may be interpreted as 55 plus 1. Correction: Encourage children to articulate and explain in full sentences alongside number lines to support the understanding of the different ways to articulate the concept. Use stem sentences to support with this and display them around the classroom.
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 10 to and from a 2-digit number. 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.