Year 5 - Maths
Apply commutative and associative laws to simplify multiplications
Multiply 3 or more numbers (commutative and associative laws)
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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 explain the use of the commutative and associative laws to rearrange and simplify calculations when multiplying three or more numbers.
Lesson Summary
You will learn to apply the commutative and associative laws to simplify multiplications of three or more numbers.
Key Notes
- Rearranging or grouping the factors in a multiplication can make it easier to solve.
Vocabulary To Learn
- efficient: Working efficiently means finding a way to solve a problem quickly whilst also maintaining accuracy.
- commutative: The commutative law states that you can write the values of a calculation in a different order without changing the solution; the result is the same. It applies to addition and multiplication.
- associative: The associative law states that it doesn't matter how you group or pair values (i.e. which we calculate first), the result is still the same. It applies to addition and multiplication.
Common Mistakes To Avoid
- Pupils continue to work only from left to right in calculations, therefore making calculations more time-consuming.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Rearranging or grouping the factors in a multiplication can make it easier to solve. Rearranging or grouping the factors in a multiplication can make it easier to solve.
2. Use this key word in a maths sentence and explain it clearly. 'efficient'
Working efficiently means finding a way to solve a problem quickly whilst also maintaining accuracy. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils continue to work only from left to right in calculations, therefore making calculations more time-consuming. Correction: Support pupils to find pairs of factors that are easy to multiply with. For example, finding factors that make a power of ten often make calculations easier as they can multiply by 10, 100 or 1000 for example at the end.
More Lessons In This Unit
- Apply the commutative and associative laws to simplify problems in a range of contexts Study Guide
- Apply the commutative and associative laws to simplify volume calculations Study Guide
- Explain the reasons for changing two-factor multiplication calculations to three-factor calculations Study Guide
- Explain the use of the commutative and associative laws when multiplying three or more numbers Study Guide
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