Greatest Common Factor and the Lowest Common Multiple?

Question

Find both the Greastest Common Factor and the Lowest Common Multiple for each set of numbers
_ how did you get the answer? Explain Please ! :S
1. 36 and 40
2. 21, 106, 63

Answer 1

the greatest common factor (GCF) is the largest common factor of two or more numbers.
the factors of
1) 36 are
(1x36),(2x18),(3x12),(4x9),(6x6)
40 are
(1x40),(2x20),(4x10),(5x8)
then look for numbers they have in
common
1,2,4,...
and pick the largest value from the
list and that is the GCF (4)

the lowest common multiple (LCM) is the smallest common multiple between 2 or more numbers
1) we found the common factors for
were 1,2,4 (but we actually ignore 1
because it is the multiplicative identity)
and choose the smallest number (2)
use these same steps for number 2
and you'll be done

Answer 2

factors of 36 - 3 X 3 x 2 x 2
factors of 40 - 2 x 2 x 2 x 5

GCF - 4

LCM - 4 x 9 x 5 x 2 = 360



factors of 21 - 3 x 7, of 106 - 2 x 53, 63 - 3 x 3 x 7

GCF - 1 ????? are you sure that the middle number isn't 105 ??

LCM - 106 x 63 = 63378

Answer 3

2 and 1 goes in 36 and 40 and 21,106 and 63 keep multipling them and you will find your answer