Year 3

Year 3

# Using doubling or halving to calculate efficiently

## Lesson details

### Key learning points

1. 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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## Worksheet

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## Starter quiz

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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.
Correct answer: You can change the order of factors and the product will be the same.
Q2.
What is the associative law in multiplication?
Correct answer: You can multiply more than two factors in any order and the product will be the same.
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
Correct answer: Multiply 6 by 5 then double
Multiply 6 x 2 then multiply 12 by 5
Q5.
8 x 4 x 10 = 4 x 10 x 8. True or false?
False

## Exit quiz

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### 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?