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Learn how to write numbers as products of prime factors. Explore why certain numbers are considered prime through interactive examples such as factorization of 36 and 28.
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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: The factors of 2 are 1 and 2 The factors of 3 are 1 and 3 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
Prime factor decomposition Write the number 36 as the product of its prime factors Think of two numbers which multiply together to give 36. We could use 2 and 18 36 2 2 18 Now ask yourself, “are these prime numbers?” Is 18 a prime number? Yes. So we can stop this part of our tree here. No. So we carry on Is 2 a prime number? 2 2 9 36 = 2 x 2 x 3 x 3 3 3 3 3 36 = 22 x 32
Prime factor decomposition Write the number 28 as the product of its prime factors Think of two numbers which multiply together to give 28. We could use 7 and 4 28 Now ask yourself, “are these prime numbers?” 7 7 4 Yes. So we can stop this part of our tree here. Is 7 a prime number? 2 2 Is 4 a prime number? 2 2 No. So we carry on 28 = 2 x 2 x 7 28 = 22 x 7
Now try some interactive questions Click here to begin
Objective Be able to write a number as the product of prime factors