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GCD and LCM

Today we learned about the Greatest Common Divisors and Lowest Common Multiples.


GCDs are the Greatest Common Divisors. This means they are the largest positive whole numbers that go into two different numbers.



This can be calculated by dividing both numbers until they are reduced to only prime numbers. Prime numbers are a type of number that can only be divided by 1 or themselves. For example, the first five prime numbers are:


2, 3, 5, 7 and 11. 1 isn't counted.



LCMs are the Lowest Common Multiples of two different numbers. This means they are the smallest possible multiples shared by both numbers.


This can be calculated in 2 ways.


The first way uses prime factors (or numbers) to work it out. All you need to do is multiply the common factors from both numbers together, but only using the most frequent or unique of the groups.



The second way is more similar to a piece of code in structure, and relies on substitution.



Overall, this is a very useful skill to learn in maths incase of a change in scale, or a substitution of measure.

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