Explain when it is efficient to use factorising or long multiplication to multiply by 2-digits
I can explain when it is efficient to use factorising or long multiplication to multiply by 2-digit numbers.
- Year 6
Explain when it is efficient to use factorising or long multiplication to multiply by 2-digits
I can explain when it is efficient to use factorising or long multiplication to multiply by 2-digit numbers.
Lesson details
Key learning points
- Multiplication can be simplified by factorising one of the factors.
- If the multiplication will involve regrouping then a written method may be more efficient.
- If the multiplication will not involve regrouping then a mental or informal method may be more efficient.
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.
Efficient / efficiently - Working efficiently means finding a way to solve a problem quickly whilst also maintaining accuracy.
Common misconception
Pupils can 'default' to using a written algorithm when learned regardless of the values of the calculation.
Consider using confident mathematicians in a race to show efficiency of different methods. Encourage pupils to 'interrogate' the values of the calculation in order to identify more efficient approaches.
Equipment
Licence
Lesson video
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