Starter quiz
- Select the prime numbers.
- 27
- 47 ✓
- 53 ✓
- 59 ✓
- 65
-
- Select the factor pairs of 30
- 1 and 29
- 2 and 15 ✓
- 3 and 10 ✓
- 10 and 4
- 5 and 6 ✓
-
- Look at the numbers below and select the composite numbers.
- 23
- 25 ✓
- 69 ✓
- 89
- 97
-
- Select the equivalent expressions which would make this equation correct. 36 × 24 =
- 36 × 1 × 23
- 36 × 12 × 2 ✓
- 36 × 12 × 12
- 36 × 6 × 4 ✓
-
- Find the expressions that are equivalent to 35 × 4 × 8
- 7 × 32 × 5 ✓
- 32 × 8 × 5
- 7 × 5 × 32 ✓
- 35 × 32 ✓
-
- Look at the equation. Find the missing number. 42 × 49 = 42 × 7 × ______
- '7' ✓
Exit quiz
- Select equivalent expressions to 21 × 30
- 21 × 5 × 6 ✓
- 21 × 6 × 5 ✓
- 30 × 7 × 4
- 30 × 7 × 3 ✓
- 30 × 3 × 8
-
- Which method is more efficient to solve 47 × 16 = ?
- Long multiplication algorithm
- Multiplying by factors ✓
-
- Which method is more efficient to solve 132 × 15 = ?
- Long multiplication algorithm
- Multiplying by factors
- Partitioning 15 into 10 and 5 ✓
-
- Which factorised example would be most efficient to solve 36 × 12?
- 36 × 1 × 12
- 36 × 6 × 2 ✓
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- Use an efficient method to solve: The Olympic event is selling tickets. Each ticket costs £32 and 29 tickets are sold in the first five minutes. What is the total amount spent? £______
- '928' ✓
- Use an efficient method to solve: 407 × 15 = ______
- '6,105' ✓
Worksheet
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Presentation
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Video
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.
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.
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.
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