Lesson 5ª

 

 

 

 

 

   

BREAKING A NUMBER DOWN IN PRIME FACTORS

 

Let's imagine we have the number 12 and we want to break it down into prime factors: one factor can be 6 and the other one 2 since we know that 12 = 2 x 6.
But 6 is not a prime number because 6 = 2 x 3.

a

When we want to break a number down into prime factors, we always start with the smaller factors.
We write the number we want to break down. To the right, we draw a vertical line and after that line, we will place the prime factors beginning by the smallest one.
Now, you have to remember when a number is divisible by 2, 3, 5, 7, 11, 13,…………….

s

x

c

Every time you break a number down using prime numbers, the last number to be written should be 1.

The answer should read like this:

v

 

As we can see, we write the number and to its right, in the form of a product (this is why we are talking about factors), we write the prime numbers with their exponents or the number of times each factor is repeated.

3.36   Observe how we have broken down the following numbers: 90, 1050, 8400 and 126348:

b

n

m

k

Sometimes, the prime numbers to be used are very big and it's hard knowing if they are actually prime.