# Bulletin Board Ideas Factoring Numbers

Math bulletin boards can be more than interesting decorations.  They can be teaching tools as well.  Factoring numbers can be both fun and challenging for students.  A bulletin board on factoring numbers can offer steps, examples and opportunities for interaction.

The simple definition for factors:

Factors are the numbers you can multiply to get another number.

The simple definition for prime numbers:

Prime numbers are the numbers that can only be numbered by themselves and one.

The simple definition for composite numbers:

Composite numbers are numbers that can be divided evenly by numbers others than 1 and itself.

Don’t do the work yourself.  Choose students to create “clouds” with these definitions printed on them.

Now it’s prime time for a rainbow.

The first five prime numbers are 2, 3, 5, 7 and 11.  Display these five numbers on a student made “rainbow.”

For example, for number 2, you can only multiply 1 x 2 or 2 x 1 for an answer of 2.  Therefore 2 is a prime number.

Have a stack of scrap paper pinned to the board, a pencil on a string and an envelope for answers.

(The answers of are 13, 17, and 19.)

You could go even more challenging of course.

What is the tenth prime number?  (29)

What is the twentieth prime number?  (71)

You could offer a reward.  It could be anything from extra credit points, to a simple announcement of names or a fun new pencil.

Not all numbers are prime.

If you can multiply more than one set of numbers to get a number, then it is not prime. It is a composite number.

For example, we can get 12 by multiplying 1 x12, or 3 x 4, or 2 x6.  That means that 1, 2, 3, 4, 6 and 12 are all factors of 12.

Note for teachers:  Of course, since we can multiply two negative numbers to get a positive, then negative 1, 2, 3, 4, 6 and 12 are also factors of 12 but if you’re just introducing factoring this may not be yet appropriate to include in your bulletin board. You decide.

Don’t leave the bulletin board “cloudy.”

We often draw factorization into trees.  Create “trees” with a number on the top and corresponding sets of leaves below it.

For example, a tree might be topped with 18.  The first two branches below it would have the numbers 1 and 18, the second two sets of branches would have 2 and 9 and the third two sets of branches would have 3 and 6.

Create a corresponding activity.

Create a corresponding individual activity with a similar tree, or better yet, have each student create their own tree and assign a certain number to all or a variety of numbers, and have each student create their own factorization tree.

Depending on the size of your bulletin board and class, you could feature them all, or rotate them each day.

Let’s look at the big picture.

A factoring bulletin board could have three clouds, each with the definitions of factoring, prime and composite.

A factoring bulletin board could have a rainbow featuring the first five prime numbers.

Lastly, a bulletin board on factoring could have trees with examples of factoring composite numbers.