1. Prime Factors

2. What are they? All composite numbers can be written as the product of prime numbers. This product is known as the prime factorisation of that number.

3. Example The prime factorisation of 12 is 2x2x3 The prime factorisation of 42 is 2x3x7

4. How to find prime factors To find the prime factorisation of 45, start by finding a factor of 45 that is also a prime number. The write 45 as a product. 45=5x9 If the last number is not prime then repeat the process until 45 is written as a product of primes. 45=5x3x3

5. Example Find the prime factorisation of 120. 120=2x60 =2x2x30 =2x2x2x15 =2x2x2x3x5 So 120=2x2x2x3x5.