Explain how to use the associative law to multiply efficiently
Lesson details
Learning outcome
I can explain how to use factorisation and the associative law to multiply efficiently.
Key learning points
- Multiplication can be simplified by factorising one of the factors.
- Look at the factors to identify which are composite numbers.
- Composite numbers can be factorised.
- Multiplication is commutative.
- Factors can be grouped in different ways and the product remains the same.
Keywords
Associative law - 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 for addition and multiplication.
Composite number - A composite number is an integer with more than two factors. All integers greater than 1 are either composite or prime.
Common misconception
Pupils can identify factors of a 2-digit number but do not consider efficiency when multiplying.
Draw attention to factor pairs and those which result in easier calculations e.g. pupils often find multiplying by 4 or 5 easier than 7, or can apply doubling when multiplying by 2
Teacher tip
This lesson assumes pupils are familiar with and increasingly fluent in recall of factors of 2-digit numbers. Consider how you might scaffold the learning if required in order to focus attention on the strategy for multiplication.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Select the prime numbers.
Q2.Look at the long multiplication below, what is the missing partial product?
Q3.Select the numbers that are factors of 12
Q4.Which of these is the complete list for the factors of 16?
Q5.What is the missing factor of 72? 1, 2, 3, 4, 6, 8, 9, 12, , 24, 36, 72
Q6.Sam and Andeep are estimating the total number of visitors across the 35 Olympic venues on one day. Each venue has on average 6,012 visitors per day. How many visitors on average, visited on this day?
Assessment exit quiz
6 Questions
Q1.Look at the numbers below and select the prime numbers.
Q2.Select the composite numbers.
Q3.Which of these are ways that 14 could be represented with its factors?
Q4.Select the expressions that are equivalent to 23 × 3 × 9
Q5.Select the expressions that are equivalent to 24 × 18
Q6.Look at the equation. Find the missing number. 29 × 33 = 29 × 3 × .
To help you plan your 6 maths lesson on: Explain how to use the associative law to multiply efficiently, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 6 maths lesson on: Explain how to use the associative law to multiply efficiently, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 2 maths lessons from the Multiplying and dividing by 2-digit numbers unit, dive into the full primary maths curriculum, or learn more about lesson planning.