Use properties of numbers and the commutative and associative laws to simplify calculations
I can use properties of numbers and the commutative and associative laws to simplify calculations.
- Year 5
Use properties of numbers and the commutative and associative laws to simplify calculations
I can use properties of numbers and the commutative and associative laws to simplify calculations.
Lesson details
Key learning points
- By rearranging a calculation it can be made easier to solve mentally
Keywords
Factor - Factors are whole numbers which exactly divide another whole number.
Commutative - The commutative law states that you can write the values of a calculation in a different order without changing the calculation; the result is the same. It applies for 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 for addition and multiplication.
Common misconception
Pupils may struggle to find factors of a number if they do not have automatic recall of their times tables.
Provide children with a multiplication grid to help pupils understand the process of the calculations, however ensure additional support is in place for children to build towards automatic recall of times tables.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Tick the factors of 20
Q2.The commutative law states that:
Q3.If a pair of brackets are placed around two factors such as in 2 × (4 × 7) = , this means:
Q4.Match the equation to the factor pairs that would be best used to help solve the calculations.
Q5.Find the product of this equation.
Q6.Find the product of this equation. 50 × 54 =
Assessment exit quiz
6 Questions
Q1.Which factors would be best to associate together to calculate efficiently? 4 × 5 × 7 = ___
Q2.Tick the three factor equations that would be equal to this two factor equation. 15 × 20 = ___ × ___ × ___
Q3.Tick the numbers that could be multiplied by a one digit number and would be equal to a multiple of 10.
Q4.Find the product of this equation.
Q5.Match the 4 factor equations that are equal to the two factor equations.
