Prime factor decomposition
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Transcript of Prime factor decomposition
Objective
Be able to write a number as the product of prime factors
Remember the prime numbers?
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ….
Here are the first ten prime numbers:
Why are they prime?
Each number has only two natural factors. In every case the two factors are the number itself and the number 1
The factors of 2 are 1 and 2
The factors of 3 are 1 and 3
Prime factor decomposition
Write the number 36 as the product of its prime factors
36
Think of two numbers which multiply together to give 36.
We could use 2 and 18
2 18 Now ask yourself, “are these prime numbers?”
Is 2 a prime number?Yes. So we can stop this part of our tree here.
Is 18 a prime number?No. So we carry on
2
2
9
3 3
2
3 336 = 2 x 2 x 3 x 3
36 = 22 x 32
Prime factor decomposition
Write the number 28 as the product of its prime factors
28
Think of two numbers which multiply together to give 28.
We could use 7 and 4
7 4Now ask yourself, “are these prime numbers?”Is 7 a prime number?
Yes. So we can stop this part of our tree here.Is 4 a prime number?No. So we carry on
2
7
22
28 = 2 x 2 x 7
28 = 22 x 7
2
Now try some interactive questions
Click here to begin
Objective
Be able to write a number as the product of prime factors
Objective
Be able to write a number as the product of prime factors