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Prime Factorisation Factor Trees

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What’s It All About? You are going to learn: How to write a number as the product of its prime factors. What skills should you have already? You need to know what it means for a number to be a prime number or a factor. You need sound multiplication skills.

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List the first few prime numbers: 2, 3, 5, 7, 11, 13, 17, List the first few prime numbers: 2, 3, 5, 7, 11, 13, 17, Write 56 as a product of its prime factors. Example = 2 2 2 7 56 is an even number so can be written as 2 something... A product is the result of multiplying. 2 is a prime number and a factor of 56 so 2 is a prime factor of 56. Is 28 a prime factor? 2 is a prime number and a factor of 56 so 2 is a prime factor of 56. Is 28 a prime factor? No, so repeat the process for 28. This is called a factor tree. All the red digits are prime factors of 56. This is called a factor tree. All the red digits are prime factors of 56.

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List the first few prime numbers: Write 90 as a product of its prime factors. Draw a factor tree: Example = 2 3 3 5 90 is an even number. 2, 3, 5, 7, 11, 13, 17, Is 45 a prime factor? No, so repeat the process for is not an even number. 45 is in the 5 times table. This is not the only possible factor tree, but any factor tree should give the same end result!

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Write 420 as a product of its prime factors. Draw a factor tree: Example = 2 2 5 3 7 2, 3, 5, 7, 11, 13, 17,

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Draw a factor tree and use it to write each of the following as the product of its prime factors Your Turn

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1. 72 Answers = 2 2 2 3 3 2, 3, 5, 7, 11, 13, 17, 19...

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2. 80 Answers 80 = 2 2 2 2 5 2, 3, 5, 7, 11, 13, 17,

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3. 75 Answers 75 = 3 5 5 2, 3, 5, 7, 11, 13, 17,

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Answers 648 = 2 2 2 3 3 3 3 2, 3, 5, 7, 11, 13, 17,

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Answers 108 = 2 2 3 3 3 2, 3, 5, 7, 11, 13, 17,

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