Prime Factors

 

A prime factor is any number which is both:

·         a factor

·         a prime number

 

eg.        factors of 24 are:

24  1, 2, 3, 4, 6, 12, 24

 

BUT prime factors are only

24  2, 3

 

Finding Prime Factors

 

METHOD 1:

·         List all the factors

·         Choose only the prime factors

 

eg. Prime factors of 36:

 

36  1, 2, 3, 4, 6, 9, 12,                  

            18, 36

 

36  2, 3

 

METHOD 2:

·         Split the number up:

 

72         = 36 x 2

= 18 x 2 x 2

= 9 x 2 x 2 x 2

= 3 x 3 x 2 x 2 x 2

 

Prime factors  2, 3

 

Prime factors of 210:

 

210              = 105 x 2

= 35 x 3 x 2

= 7 x 5 x 3 x 2

 

Prime factors 2, 3, 5, 7