Topic Four (1.4): Finding HCF and LCM using Prime Factorisation
Introduction
This topic shows how Prime Factorisation can be useful when finding the Highest Common Factor (HCF) and Lowest Common Multiple (LCM).
Warm Up
We will start this lesson revisiting the game played recently, to recap prime factorisation:
EXPLORE – Prime factorisation - pairs activity (MyMaths) Links to an external site. [Not available on sample course]
Working through your course book
- Start by watching this video, which introduces prime factorisation:
- Read and make notes on page 16, copying out the worked example, if you think it will help you.
- Now see if you can answer the Band 2, questions 11-13 on page 17.
- If you would like more practice, then work through these lessons on the MyMaths website:
EXPLORE – Highest common factors (MyMaths) (slides 7-9) Links to an external site. [Not available on sample course]
EXPLORE – Lowest common multiples (MyMaths) (slide 3 only) Links to an external site. [Not available on sample course]
- You may also want to watch the following Corbettmaths video:
Plenary
You have a choice: you can end this lesson by playing a maths game, or watching a video (or even both, if you have time!)
Game-time!
It helps if you can multiply the numbers together quickly, so try this game on the fastest speed:
PLAY – Snakey Solver (MyMaths) Links to an external site. [Not available on sample course]
Video
It is no coincidence that Periodica Cicada only emerge en masse during prime-numbered years. This video gives a possible explanation for this:
WATCH – Primed for Survival (Twig) [Not available on sample course]
Support activities for this topic
The Band 1, questions 2-6 on page 17 will help build your skills on this topic.
Extension activities for this topic
If you would like more of a challenge on this topic, go to page 18 and attempt the Band 3 questions.