This video is a quick reminder of highest common factor HCF & lowest common multiple LCM for GCSE maths, and is aimed at around grade 5.
– stop the video
– work through the questions
– compare your solutions
I hope the video helps and please do leave a comment – thanks!
Download a copy of the questions here:
Here’s a copy of the written answers:
1. Write 210 as a product of its prime factors
2. Find the highest common factor (HCF) of 42 and 98
3. Find the lowest common multiple (LCM) of 42 and 98.
4. Find the highest common factor (HCF) of 15, 24 and 27
5. Find the lowest common multiple (LCM) of 15, 24 and 27
6. 3240 = 2² x 3³ x 5 3780 = 2² x 3² x 5 x 7
(i) Find the highest common factor (HCF) of 3240 and 3780
(ii) Find the lowest common multiple (LCM) of 3240 and 3780
These types of questions appear in all the main GCSE exam boards – Edexcel, AQA, OCR and Educas – and are fairly common for non calculator papers.
- Always use a factor tree to find the prime factors
- Divide by 2, then 3, then 5 to make your working easier to follow
- If you have time, check your prime factors multiply to the original number
- A venn diagram can be a useful way of showing your results
Here’s other posts that also might be of interest:
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