### Home > CC1 > Chapter 3 > Lesson 3.2.4 > Problem3-130

3-130.

Find the greatest common factor and the least common multiple of each of the following sets of numbers.

1. $12$ and $7$

• $7$ is a prime number, so its only factor other than itself is $1$.

Their greatest common factor is $1$. Can you find their least common multiple?

1. $3, 15$, and $9$

• To find the least common multiple, try finding multiples of $15$ and checking
whether they are also multiples of $3$ and $9$.

The least common multiple is $45$. Try finding the greatest common factor.

1. $20$ and $30$

• $10$ is a factor of both of these numbers.