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.
Top Tips!
- 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:
How to work out the HCF and LCM using factor trees
Speed Distance Time; mid level GCSE mathematics questions
How to factorise equations containing algebra terms
Simplify an algebra fraction using factorising
Expand brackets and simplify; mid-level GCSE maths algebra
Reverse percentage; prices in a sale
How To Work Out Reverse Percentages; GCSE mathematics
Please do leave a comment below if you are not sure. Alternately you can view my YouTube channel and leave a comment there – I’ll always try to respond as quickly as possible.
Watch on YouTube:
Highest Common Factor HCF & Lowest Common Multiple LCM
I’d really appreciate a like, if you found it useful! If you subscribe to the channel, you’ll also be notified of new uploaded videos 🙂
As a 50yr old Electronics Engineer doing some extra curricular aviation studies as you are never too young! – this was a good refresh and showed me a way I was never taught by using a vein diagram. Far better than the methods described in a rather expensive aviation tutorial package – I knew the answers but couldn’t remember the exact method. thanks
Glad to help and all very best with your studies. Kind Regards S