Prime decomposition

Every composite number can be expressed (or written) as a product of its prime factors.

Remember that factors are numbers you multiply together, the number you get from multiplying to factors together is a product.

Factor trees

A factor tree can be used to find the prime factors of a composite number.

We draw our tree with the branches being the factors of our number. The end of the branches are where the prime numbers sit.

Let's have a go...

Together let's draw a factor tree for the number 24

Our factor tree has shown that the prime factors of 24 are 2 and 3.

We can use this tree to write our original number as a product of each terminating branch (the last number on each branch). This means that 24 = 2 x 2 x 2 x 3.

Using our knowledge of indices from the previous lesson can you think of a simplified (easier) way of expressing this?

Let's do a couple more together by completing the following trees and expressing (writing) the original number in prime factor form.

Now it is your turn! Start working on the below questions from your ticksheet.

Page updated

Google Sites

Report abuse