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.
Combine the factors, eliminating duplicates.
2 x 3 x 5 x 7 = 210, the LCM.
Two pairs of numbers with a GCF of 26 are 26 & 52 or 52 & 78
(4,8) and (8,12) both have a GCF of 4.
The gcf of 24 and 36 is 12
Co-prime numbers
4 and any multiple of 4 have a GCF of 4.
The GCF of the given numbers is 8
7 and any multiple of 7 Any multiples of 7 that differ by 7
Any multiples of 4 that differ by 4.
13 and 26, for example.
The two that are relatively prime.
5 and 105 and 1510 and 15
7 and 14 14 and 21 7 and 21