Prime Factors up to 100: Lesson for Kids

Lesson Transcript
Instructor: Mark Boster

Dr. Mark. A. Boster received his doctorate in Educational Leadership from Liberty University and conducted his research in gender roles in award-winning children’s books. He has over 24 years of experience in education at Columbus City Schools holding roles such as curriculum coordinator and classroom teacher.

Prime factors are needed when you want to take a number down to its bare basics. Sometimes in math, you need to find the prime factor in order to do other types of equations. This is a step between what you know and what you will know! Updated: 05/21/2020

Prime Factors

In art class, Mrs. Thatcher wanted the students to draw trees. Some trees looked like clouds with a trunk, but Shantea wanted to draw a tree in the winter. She drew the trunk and then added straight lines connected to each other to look like branches.

Later that day, in math, the students learned to factor numbers. 'Hey,' Shantea said, 'It looks like my tree with Mrs. Thatcher!' And they did!

A prime number is a whole number larger than 1 that can only be divided by 1 and itself. An example of this would be the number 7. You can't divide anything into 7, except 7 and 1.

A factor is any number you can multiply by another number to get a third number. In the equation 4 x 5 = 20, both 4 and 5 are factors of 20.

Bet you can guess what is coming next. A prime factor is a factor that is also a prime number. All whole numbers can be factored into prime numbers.

These are all the prime factors under 100:

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97.

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Coming up next: Word Problems: Greatest Common Factor & Least Common Multiple

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  • 0:04 Prime Factors
  • 1:33 Factoring Numbers on a Tree
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Factoring Numbers on a Tree

How about using some trees? Well, they sort of look like little number trees.

Let's see how to factor a number. How about the number 20? The factors of 20 can be 4 and 5 (since 4 x 5 = 20), or 2 and 10 (because 2 x 10 = 20). Let's use the 4 and 5 for now. Let's get that down to prime factors.

Can you divide anything into 4 or 5 other than 1 and the number itself? Well, not the 5, so 5 is one of the numbers we're looking for.

The 4 you can factor further because 2 x 2 = 4.

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