Year 9: Prime factorisation

What is Prime factorisation?

Prime factorisation is the process of breaking down a number into its prime factors. A prime number is a whole number greater than 1 that has only two divisors: 1 and itself (e.g., 2, 3, 5, 7, 11).

A composite number is any whole number that can be formed by multiplying prime numbers.

How to do it:

1. Start with the number you want to factorise. Let's use the number 36 as an example.
2. Divide the number by the smallest prime number that divides it evenly. 36 is divisible by 2. So, 36 / 2 = 18.
3. Repeat the process with the result. Continue dividing by prime numbers until you are left with only prime numbers.
4. Write the number as a product of its prime factors, using exponents where necessary. 36 = 2² x 3²

Example: Prime factorising 60

1. 60 / 2 = 30
2. 30 / 2 = 15
3. 15 / 3 = 5
4. 5 / 5 = 1

Therefore, the prime factorisation of 60 is 2² x 3 x 5.