How do you work out GCF of 80 and 100?

Answer 1

The factors of 80 are:

1, 2, 4, 5, 8, 10, 16, 20, 40, 80

The factors of 100 are:

1, 2, 4, 5, 10, 20, 25, 50, 100

The common factors are:

1, 2, 4, 5, 10, 20

The Greatest Common Factor:

GCF = 20

Answer 2

-- Make a list of all the factors of 80.

-- Make a list of all the factors of 100.

-- Collect the group of numbers that are on both lists. Those are the common factors.

-- Find the biggest number in the group. That's the greatest common factor.

-- If it's not 20, then go back to the beginning and try again.

You should use exactly this same process to find the greatest common factor of any

two numbers, although it won't always be 20. I'm surprised that you still have to ask.