How do you find the factors of a large number? These pictures below will help explain how to do so by using both factor trees and division tables.
Factor Trees
First, you have to start with a number, say, 80. Start by writing it at the top of your page. Next, think of any 2 numbers that multiply to equal 80. Maybe 10 and 8? Write these 2 numbers below in a branch-like formation.
Next, think of any 2 numbers that can multiply to equal 10, and 2 numbers that equal 8. For 10, I’m going to use 5 and 2. For 8, I’m going to use 4 and 2. Branch off these numbers out of 10 and 8. Now that those numbers are written down, you have to look and see if you can expand on any numbers.
We can only expand on 4, which goes to 2 and 2. Now, list all the numbers at the bottom of the tree.
Here, we can finally see all the factors that multiply together to equal 80.
Division Tables
First, we’re going to start with a number, 80. Write this down and then draw a little fish hook underneath it. Write a 2 next to it, and divide 80 by 2.
That equals 40, so write 40 under it. Continue doing this until you eventually cannot divide the number anymore. The list of numbers on the side of the tables are the prime factors in the number. In this case, I only divided by prime numbers.
