The HCF and LCD Calculator

If you've read the "Brotherly Love and LCD" chapter of "The Mean and Vulgar Bits", you'll know that when you start playing with adding and subtracting fractions, you often need to know the Lowest Common Denominator (also known as the Lowest Common Multiple ). This means that you have any two numbers and you want to know the lowest number that they'll both divide into. If you have 12 and 16, their LCD is 48. However if you have 9 and 14, the LCD is 126.

The "Bug Buster" chapter deals with the Highest Common Factor - this is really handy to know for smashing big fractions to bits. This time you have two numbers and you want to know what's the biggest number that will divide into both. So if you have 35 and 49 their HCF is 7. If you have 91 and 94 the HCF is 1. (Quite often it's just 1 !)

Try putting any two numbers in here then hitting the button. It'll give you the LCD and HCF straight away. Pity you can't take this one into exams eh?

Find out all you need to know about HCFs and LCDs in
The Mean and Vulgar Bits!

First Number
Second Number

Lowest Common Multiple
Highest Common Factor

If you find the LCM and HCF of two numbers, and multiply them together, it's the same as multiplying the two numbers together!

So if your numbers are 18 and 42, the LCM=126 and the HCF=6.

18 x 42 = 756 and 126 x 6 = 756

Thanks to SHING FUNG (age 8) from Hong Kong who told us this!

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