Year 3 - Maths
Bridge 100 by adding or subtracting a single-digit number
Bridging 100: counting on and back in 10s, adding/subtracting multiples of 10
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 will find pairs of number that compose 100. They will position 3-digit numbers on a number line and estimate their position on unmarked number lines. They will compare and order 3-digit numbers.
Lesson Summary
You will learn to bridge 100 by adding or subtracting a single-digit number.
Key Notes
- Knowledge of number facts to 20 can support calculation across the 100 boundary.
- If 8 plus 7 is equal to 15 then 98 plus 7 is equal to 90 plus 15 which equals 105
- Knowledge of place value can help when counting forwards across the 100 boundary.
Vocabulary To Learn
- Bridging: A strategy which uses addition or subtraction to cross a number boundary.
- Partition: The act of splitting an object or value down into smaller parts.
Common Mistakes To Avoid
- Pupils may not partition numbers in efficient ways to add and subtract them.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Knowledge of number facts to 20 can support calculation across the 100 boundary. If 8 plus 7 is equal to 15 then 98 plus 7 is equal to 90 plus 15 which equals 105.
2. Use this key word in a maths sentence and explain it clearly. 'Bridging'
A strategy which uses addition or subtraction to cross a number boundary. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils may not partition numbers in efficient ways to add and subtract them. Correction: Encourage pupils to add or subtract to make 100 (e.g. when calculating 103-7, subtract 3 to equal 100, then subtract 4 to equal 96).
More Lessons In This Unit
Browse all guides in the Year 3 Maths guide library.