How_To_Be_Good_At_Math

34 NUMBERS •^ PRIME FACTORS

Prime factors

A factor of a whole number that is also a prime number is called a prime factor.

One of the special things about prime numbers is that any whole number is either

a prime number or can be found by multiplying two or more prime factors.

All whole numbers

can be broken down

into two or more

prime factors.

We start by seeing if we can divide 30 by 2,

the smallest prime number. We can divide 30

exactly by 2, and 2 is a prime number, so we can

say 2 is one of 30’s prime factors.

Now let’s look at 15, the factor pair of 2 in the

last step. It’s not a prime number, so we have

to break it down more. We can’t divide it exactly by

2, so let’s try another number.

We can divide 15 exactly by 3 and get 5. Both

3 and 5 are prime numbers, so they must also

be prime factors of 30.

Finding prime factors

Prime numbers are like the building blocks of numbers, because

every number that’s not a prime can be broken down into

prime factors. Let’s find the prime factors of 30.

So, we can say that 30 is the product of

multiplying together three prime factors –

2, 3, and 5.

30 ÷ 2 = 15 15 ÷ 2 =?

15 ÷ 3 = 5 30 = 2 x 3 x 5

Prime factors for internet security

When we send information over the internet, it’s turned

into code to keep it secure. These codes are based on

prime factors of very large numbers, which fraudsters

would find really difficult and time-consuming to find.

REAL WORLD MATHS

Prime factors have a

green circle round them

2 and 15 are factors of 30 2 is not a factor of 15

3 and 5 are factors of 15 2, 3, and 5 are prime factors of 30

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