New
New
Year 5

# Multiply a 2-digit number by a 1-digit number using expanded multiplication (regrouping 1s to 10s)

I can use expanded multiplication to record regrouping from the 1s to the 10s

New
New
Year 5

# Multiply a 2-digit number by a 1-digit number using expanded multiplication (regrouping 1s to 10s)

I can use expanded multiplication to record regrouping from the 1s to the 10s

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## Slide deck

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## Lesson details

### Key learning points

1. If the product of the ones digits is greater than 10, you regroup ten ones into one ten.
2. If the product of the ones digits is greater than ten, the partial product will be a 2-digit number.
3. There are similarities between the representations of multiplication.

### Common misconception

Pupils may not align or regroup correctly leading to an inaccurate calculation.

Continue to ask what each digit that has been recorded represents. Demonstrate the regrouping using base ten blocks to help.

### Keywords

• Regrouping - The process of unitising and exchanging between place values is known as regrouping.

• Expanded multiplication - Expanded multiplication is a way of recording a calculation focusing on partitioning one or more factors and showing partial products.

Ensure children are able to generalise that if the ones digits is greater than ten, the partial product will be a 2-digit number.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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## Worksheet

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## Starter quiz

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### 6 Questions

Q1.
21 ones are equivalent to __________.
Correct answer: 2 tens and one one
2 tens and 1 ten
1 ten and 2 ones
2 ten and 2 ones
Q2.
Look at this equation. The numbers highlighted in purple are known as .
products
partial products
Correct answer: factors
addends
Q3.
Select the correct representation for this multiplication.
Picture 2
Picture 3
Correct answer: Picture 4
Q4.
The multiplication is: 73 × 2 Which short multiplication shows this correctly?
Correct answer: Picture 1
Picture 2
Q5.
Which representation will require regrouping?
A
Correct answer: B
C
Q6.
Match the representations A, B and C to the correct multiplication equation.
Correct Answer:A,13 × 3

13 × 3

Correct Answer:B,3 × 14

3 × 14

Correct Answer:C,3 × 11

3 × 11

## Exit quiz

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### 6 Questions

Q1.
Look at the image. The arrows are pointing to __________.
factors
products
Correct answer: partial products
addends
Q2.
Select the correct expanded method shown by this representation.
picture 1
Correct answer: picture 2
Q3.
Sofia believes that you always have a 1-digit partial product when multiplying a 2-digit by a 1-digit number. What do you think?
This is always true.
Correct answer: This is sometimes true.
This is never true.
Q4.
Which multiplication will need regrouping in the ones column only?
71 × 3
10 × 3
Correct answer: 17 × 3
77 × 3
Q5.
Using Lucas’s grid model, fill in the gap for the expanded multiplication.
Correct Answer: 32, 3 2 , Thirty two, Thirty-two
Q6.
Use expanded multiplication to calculate: 3 × 19
Correct Answer: 57, fifty-seven, Fifty-seven