We learnt that there are several ways that we can use to find HCF of numbers.

Question: Find the HCF of 40, 36 and 24
Here are the various methods used by some of you:

**Method 1**: Listing - this is the simplest way to do; however, you risk missing out numbers as you test the given number with different factors. This method could be time-consuming when you are handling large mumbers

**Method 2**: Listing pairs of factors. When systematically carried out, the highest common factor could be easily surfaced. This method could be time consuming as you are 'obliged' to list down all the pairs in order to find the largest factor common amongst the given numbers.

**Method 3: **Using "grouped' repeated division. This is one of the faster methods. Remember to apply the "prime factorisation" protocol, i.e. start with the smallest prime number.

**Method 4 (Preferred) & Method 5 (Preferred): **Carry out the

**prime factorisation** for each number. Express the product of these factors in

**index notation**. Express in index notation and surface factors that are common across the numbers. The product of these factors will give the HCF of the numbers.

*Method 4*

*Method 5*

Making Connections