Topic Five (1.5): LCM and HCF
Introduction
The lowest common multiple (LCM) of two numbers is the smallest number that occurs in both times tables. The highest common factor (HCF) of two numbers is the largest number that will divide into both.
Helpful hints
Using a Venn diagram can really help with these questions, the example in the text book is worth studying carefully.
Working through your course book
You will be shown how to find the HCF and LCM of two numbers by using prime factors.
- Go to the MyMaths 2B digital book and watch the videos on page 13.
- Now read through the example on page 12, which shows the two ways of finding the HCF and LCM of two numbers.
- Answer the questions on page 13.
- If you would like more practice, work through these lessons on the MyMaths website:
You may also want to watch the following MathsWatch videos and work through the interactive questions using the tab at the top of the screen:
WATCH - Lowest Common Multiple (MathsWatch) Links to an external site.
WATCH - Highest Common Factor (MathsWatch) Links to an external site.
Support activities for this topic
The MyMaths 2A digital book introduces these topics at a slower pace. If you'd like to take more time to understand these, look at pages 8–9 for more support.
Extension activities for this topic
The MyMaths 2C digital book provides extension material in their problem-solving questions.
If you would like more of a challenge on this topic, go to page 9 of the MyMaths 2C digital book and attempt questions 6–8.
Writing a number in terms of its prime factors can be used to calculate the HCF and LCM. To learn this skill study pages 6 and 7 Links to an external site..