How do you find the GCF of 20 and 30?
The preferred technique is to factor each number then multiply all common factors together to find the greatest common factor.
First factor 20 down to its prime factors.
Second factor 30 down to its prime factors
The common factors are 2 and 5.
The greatest common factor is
There are shortcuts that often work however
20 can be easily factored into
30 can be easily factored into
10 can then be easily be seen as the greatest common factor.