Year 2 - Maths
Find 10 more or less than 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 find 10 more or 10 less than a two-digit number.
Key Notes
- When finding 10 more or 10 less than any two-digit number, the ones digits does not change.
- When finding 10 more than a number below 100, the tens digit increases by one.
- When finding 10 less than a number below 100, the tens digit decreases by one.
Vocabulary To Learn
- 10 more: 10 more than is when there is a greater amount by 10 than another item in the set.
- 10 less: 10 less than is when there is a smaller value by 10
- Increase: Make something bigger (in size or quantity).
- Decrease: Make something smaller (in size or quantity).
Common Mistakes To Avoid
- Children may default to counting in ones to find ten more or ten less.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When finding 10 more or 10 less than any two-digit number, the ones digits does not change. When finding 10 more than a number below 100, the tens digit increases by one.
2. Use this key word in a maths sentence and explain it clearly. '10 more'
10 more than is when there is a greater amount by 10 than another item in the set. 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 default to counting in ones to find ten more or ten less. Correction: Use representations that highlight the structure of the base 10 system, e.g. Base 10 blocks/one hundred squares, and also 'dual counting' to support understanding of 'unitising', i.e. that using 'ten' as a unit can help to calculate more efficiently.
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 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
- 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.