Year 3 - Maths
Choose the most efficient strategy to subtract from a 3-digit number
Informal and mental strategies for adding and subtracting two 3-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 two 3-digit numbers using partitioning, adjusting, redistribution and bridging.
Lesson Summary
You will learn to choose the most efficient strategy to subtract from a 3-digit number.
Key Notes
- By looking carefully at the minuend and subtrahend, we can choose the most efficient subtraction strategy.
- When numbers are close together, finding the difference is the most efficient strategy.
- Sometimes, we can use known addition facts to make finding the difference even more efficient.
Vocabulary To Learn
- Minuend: The minuend is the number being subtracted from.
- Subtrahend: A subtrahend is a number subtracted from another.
- Difference: The difference is the result after subtracting one number from another.
- Partition: Partition is the act of splitting an object or value down into smaller parts.
Common Mistakes To Avoid
- Children will often reverse the minuend and subtrahend because they don't always appear in the order that they would in an expression.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
By looking carefully at the minuend and subtrahend, we can choose the most efficient subtraction strategy. When numbers are close together, finding the difference is the most efficient strategy.
2. Use this key word in a maths sentence and explain it clearly. 'Minuend'
The minuend is the number being subtracted from. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Children will often reverse the minuend and subtrahend because they don't always appear in the order that they would in an expression. Correction: Ensure that the children spend time understanding the context, either through discussion of the problem or through visual representations such as bar models. It's also worth spending time on vocabulary by playing fun word games or charades.
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
- Add two 3-digit numbers using partitioning Study Guide
- Choose the most efficient strategy to add two 3-digit numbers 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
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