In order to help parents reinforce ideas learned in school and in tutoring, Academics Plus, Inc. is offering a Lesson series on our blog that demonstrates basic concepts using items you can find around the house.

**Greatest Common Factor**

The greatest common factor of two numbers is the largest number that can be divided into both numbers evenly (also known as a factor of both numbers). Sound confusing? This simple exercise should help both you and your child understand the subject.

__What you will need:__

- 2 Newspaper pages
- A table
- A pen/marker

__Directions:__

1. Clear out a space on your table and separate the newspaper pages.

2. Begin by finding the greatest common factor of 18 and 24. Write one of each of the following equations at the top of a newspaper page:

3. Ask your child to divide both of these numbers by a low prime number like two to fill in the equation and begin writing a factor tree. Factor trees will look like this:

4. Once your child has written the factor tree, ask him or her to find all the common numbers between each set of factors at the end of both factor trees as shown by the highlighted numbers above.

5. When your child has chosen the numbers, write one number from each pair and put a multiplication symbol between them. For example:

Then have your child multiply the numbers together (with larger numbers, it is likely that more than two factors will need to be multiplied together to get the GCF). The result is the greatest common factor.

6. Complete steps 1-5 with the following number sets:

12, 24

18, 27

56, 24

**Reader Question:** Can you think of another way to find the greatest common factor? Share it in the comments!