
What are natural numbers?
1, 2, 3, ....

Find LCM of 6 and 15.
note:what is the smallest number they have in common
 6: 6, 12, 18, 24,30, 36
 15: 15, 30, 45, 60

Find the LCM of 6 and 15
note: the smallest common number by prime factorization

What are rational numbers?
 Numbers that end or terminating, repeating decimal
 ex: 3.5, 0.454545...., 0.375, 3, 11, 4/5,

* two positive integers, the product is positive
ex: 9*2
18

two real numbers with different signs is negative
ex: 4*3=
4*1=

* two negative integers the product is positive
ex: 4*2=
8

write 24/30 in lowest terms
 24 2*2*2*3
 40 2*2*2*5
 cross out common factors; left with 3/5

