Using doubling or halving to calculate efficiently
Using doubling or halving to calculate efficiently
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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.
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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