Year 3

# Using doubling or halving to calculate efficiently

Year 3

# Using doubling or halving to calculate efficiently

## Slide deck

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## Lesson details

### Key learning points

- In this lesson, we will use doubling and halving skills to efficiently calculate multiplication and division involving a factor of 2.

### 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.

## Video

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### 5 Questions

Q1.

What is the commutative law in multiplication?

If you change the order of factors and the product will change too.

Q2.

What is the associative law in multiplication?

You can multiply three factors in a certain order.

You should not multiply more than two factors.

Q3.

Which law do you use when multiplying 2 x 5 x 6?

commutative law

Q4.

When multiplying 6 x 2 x 5, which is the most efficient order?

Multiply 2 by 5 then multiply 10 by 6

Multiply 6 x 2 then multiply 12 by 5

Q5.

8 x 4 x 10 = 4 x 10 x 8. True or false?

False

### 5 Questions

Q1.

To multiply by 4, you can double and double again.

False

Q2.

To divide by 4, you can halve then halve again.

False

Q3.

What is 72 divided by 4?

288

36

Q4.

What is 17 x 4?

136

34

Q5.

To multiply by 8 you can multiply by 2, 3 times. This is the same as multiplying by 6.

True