HOW TO FIND greatest common factor?

Answer 1

-- List factors of first number.

-- List factors of second number.

-- Make short list of all numbers on both factor lists.

-- Biggest number on short list is greatest common factor of both numbers.

Answer 2

The method taught in school involves factoring each number into prime factors, and then checking what factors are in common. A much more efficient method, especially for large numbers, is Euclids algorithm, which I'll illustrate with an example. What's the greatest common factor of 14 and 10?

gcf(14, 10) = gcf(10, 4) (where 4 is the remainder of the division of 14 by 10)

gcf(10, 4) = gcf(4, 2) (where 2 is the remainder of the division of 10 by 4)

gcf(4, 2) = gcf(2, 0) (0, once again, is the remainder of the division)

gcf(2, 0) = 2 (the greatest common factor any number with zero is that first number, in this case, 2)

Answer 3

Example: 30 and 42

Factor them.

2 x 3 x 5 = 30

2 x 3 x 7 = 42

Select the common factors.

2 x 3 = 6, the GCF

Answer 4

Example: 30 and 42

Factor them.

2 x 3 x 5 = 30

2 x 3 x 7 = 42

Select the common factors.

2 x 3 = 6, the GCF