Year 3

Using doubling or halving to calculate efficiently

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.

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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?
Correct answer: associative law
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
Correct answer: True

5 Questions

Q1.
To multiply by 4, you can double and double again.
False
Correct answer: True
Q2.
To divide by 4, you can halve then halve again.
False
Correct answer: True
Q3.
What is 72 divided by 4?
Correct answer: 18
288
36
Q4.
What is 17 x 4?
136
34
Correct answer: 68
Q5.
To multiply by 8 you can multiply by 2, 3 times. This is the same as multiplying by 6.
Correct answer: False
True