Factors, Primes & Composite Numbers

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Transcript Factors, Primes & Composite Numbers

Today we will determine the
prime factors of all the
numbers through 50
Prime Number – a number that has only two
factors, itself and 1.
Factor – a number that divides evenly into
another.
Composite number – a number that has more
than two factors.
Definition
Product – An answer to a
multiplication problem.

7 x 8 = 56
Product
Definition
Factor – a number that is
multiplied by another to give
a product.

7 x 8 = 56
Factors
Definition
Factor – a number that
divides evenly into another.

56 ÷ 8 = 7
Factor
Remember you learned
th
factors in 4 grade?
What are the factors of 42?
6 x 7 = 42
6&7
What are the factors?
42 ÷ 7 = 6
63 ÷ 9 = 7
7&6
9&7
Definition
Prime Number – a number
that has only two factors, itself
and 1.

7
7 is prime because the only numbers
that will divide into it evenly are 1 and 7.
Examples of Prime
Numbers
2, 3, 5, 7, 11, 13, 17, 19
Special Note:
One is not a prime number.
Definition
Composite number – a
number that has more than two
factors.

8
The factors of 8 are 1, 2, 4, 8
Examples of Composite
Numbers
4, 6, 8, 9, 10, 12, 14, 15
Special Note:
Every whole number from 2 on is
either composite or prime.
Our Lonely 1
It is not prime
because it does
not have exactly
two different
factors.
It is not
composite
because it does
not have more
than 2 factors.
Special Note:
One is not a prime nor
a composite number.
Definition
Prime Factorization – A way
to write a composite number as
the product of prime factors.

2 x 2 x 3 = 12
So the prime numbers
are 2 and 3
Why is it important to know
about Prime Factorization?






It will be in the CST.
It helps you understand multiplication and division
better.
A prime number can only be divided by 1 or itself, so
it cannot be factored any further!
Every other whole number can be broken down into
prime number factors.
It is like the Prime Numbers are the basic building
blocks of all numbers.
What are other reasons to know the all the
prime factors to 50?
Let’s “draw” some Prime
factor trees!
12
1.
2.
2
Prime!
x
6
3.
2
x
3
x
2
4.
5.
2, 2, & 3
Steps!
Write down the composite
number.
Choose factors that equal the
composite number (not the
number times 1)
Keep breaking the number down
until all you have are prime
numbers!
Remember to circle your prime
numbers!
Write down your prime numbers
from smallest to greatest!
Let’s “draw” some Prime
factor trees!
16
1.
2.
4
x
4
3.
2 x 2x 2
x 2
4.
5.
2, 2, 2, & 2
Steps!
Write down the composite
number.
Choose factors that equal the
composite number (not the
number times 1)
Keep breaking the number down
until all you have are prime
numbers!
Remember to circle your prime
numbers!
Write down your prime numbers
from smallest to greatest!
Let’s “draw” some Prime
factor trees!
25
1.
2.
5
x
5
3.
5&5
4.
5.
Steps!
Write down the composite
number.
Choose factors that equal the
composite number (not the
number times 1)
Keep breaking the number down
until all you have are prime
numbers!
Remember to circle your prime
numbers!
Write down your prime numbers
from smallest to greatest!
Let’s review what we learned!
 What

numbers that have more than two factors.
 What

are composite numbers?
are prime numbers?
a number that has only two factors, itself and 1.
 What
is the prime factorization of 20?