Year 3 - Maths
Add two 3-digit numbers using partitioning
Informal and mental strategies for adding and subtracting two 3-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 will add and subtract two 3-digit numbers using partitioning, adjusting, redistribution and bridging.
Lesson Summary
You will learn to add two 3-digit numbers using partitioning.
Key Notes
- Partitioning can be used to add 3-digit numbers
- Unitising means we can use known facts to add larger numbers. For example, 370 + 260 is equal to 37 tens add 26 tens.
Vocabulary To Learn
- Addend: An addend is a number added to another.
- Sum: The sum means the total when the numbers are added together.
- Unitising: Unisiting means treating groups that contain the same number of things as 'ones' or 'units'.
Common Mistakes To Avoid
- Pupils may not understand that a tens counter has a value of ten. For example, they may think that 14 tens and 11 tens make 25 altogether, forgetting to convert 25 tens into 250.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Partitioning can be used to add 3-digit numbers. Unitising means we can use known facts to add larger numbers. For example, 370 + 260 is equal to 37 tens add 26 tens.
2. Use this key word in a maths sentence and explain it clearly. 'Addend'
An addend is a number added to another. 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 understand that a tens counter has a value of ten. For example, they may think that 14 tens and 11 tens make 25 altogether, forgetting to convert 25 tens into 250. Correction: Encourage counting in tens using counters to begin with. Move onto modelling questions using base ten so the children can count the tens blocks.
More Lessons In This Unit
- Add 2 and 3-digit numbers by redistributing Study Guide
- Add two 3-digit numbers using adjusting strategies Study Guide
- Choose the most efficient strategy to add two 3-digit numbers Study Guide
- Choose the most efficient strategy to subtract from a 3-digit number Study Guide
- Subtract 2 or 3-digit numbers using partitioning and bridging a multiple of 10 Study Guide
- Subtract 3-digit multiples of 10 by finding the difference between them Study Guide
- Subtract a pair of 2-digit numbers by finding the difference Study Guide
- Use addition and subtraction to solve problems in different contexts Study Guide
- Use addition and subtraction to solve problems involving bar charts, pictograms and tables Study Guide
Browse all guides in the Year 3 Maths guide library.