Year 5

# Doubling and halving strategies

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## Lesson details

### Key learning points

- In this lesson, we will explain and model mental strategies for doubling and halving by using our understanding of multiplication and division. We will also use our doubling and halving strategies to multiply and divide by four and eight. By the end of this lesson, we would hope that everyone will be confident in explaining how to multiply and divide by four and eight by using strategies of doubling and halving.

### Licence

This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

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### 5 Questions

Q1.

Look at the value represented by the place value grid below. If I multiply the number by 100, what will the new product be?

2,400,000

24,000

Q2.

In mathematics, we use the term 'product' regularly. Look at the following calculation and identify which of the numbers listed would be classified as the product. 30 x 2 x 10 = 600

10

2

30

Q3.

Which of the facts can I derive from the representation below?

2 x 40 = 80

20 x 4 = 80

80 ÷ 2 = 40

None of the above

Q4.

Using the area model below, can you identify which of the number sentences is correct?

30 x 40 = 3 x 40 x 100

30 x 40 = 30 x 4 x 1

30 x 40 = 30 x 40 x 100

Q5.

When multiplying and dividing, we regularly use the terms 'greater than' and 'less than'. Which of the following statements has used the symbols incorrectly?

10 x 3 x 2 = 15 x 4

234 > 219

28194 < 28914

### 5 Questions

Q1.

The strategy of separating a number into its individual units of value is commonly known as?

Approximation

Guessing

Rounding

Q2.

Half of 24 is also the same as:

240 ÷10

72 ÷ 3

96 ÷ 2

Q3.

The bar model below is used to help divide or multiply numbers. What number should be placed in the top white boxes?

12

40

6

Q4.

Which of the following number sentences will help you to solve the calculation 25 x 8?

100 x 4

250 x 80

50 x 8

Q5.

Which derived fact helps me to mentally solve 240 ÷ 5?

120 ÷ 10

120 x 10

48 ÷ 10