Transcript prime number - SCHOOLinSITES

Prime numbers
Composite numbers
Neither prime nor composite
How to know?
Prime and composite numbers
are all about multiplication
Multiplication math vocabulary:
The two numbers being multiplied together
are each called
factors.
The answer in a multiplication problem is
called the
product.
Multiplication
factor x factor = product
Prime Numbers
To determine
if a number is a prime
number,
place it in the product position.
Factor X Factor = Product
Is this number a
prime number?
Prime Numbers
1.
2.
3.
Must have ONLY two possible, unique
factors. (Both factors cannot be the same.)
One factor must be 1.
One factor must be a whole number, but
not 0 or 1.
Factor
same number
as the product,
but not 0 or 1.
X
Factor
1
=
Product
same number as
one of the factors,
but not 0 and not 1
Whole numbers
In case you forgot:
Whole numbers are the
the number 0, and the natural
numbers which start at positive one— {0,
1, 2, 3...}
Prime Numbers
3
X
1
=
3
same number
as the product,
same number as
one of the factors,
but not 0 or 1.
but not 0 and not 1
3 is a prime number.
1.
There are ONLY two possible, unique factors.
(No other two numbers multiplied together have a product
of 3 and both factors are different numbers.)
2. One factor is 1.
3. One factor is a whole number, but not 0 or 1.
Prime Numbers
misconception is
that odd numbers
are always prime numbers
A common
but, that’s not true.
Prime Numbers
Some odd
numbers,
like 9 have more than
two factors.
9 x 1 = 9,
but so does
3 x 3.
Consequently, 9 is not a prime number.
Prime Numbers
51 is tricky!
It is an odd number.
It looks like only 51 x 1 = 51, but
17 x 3 = 51 too.
51 is not a prime number.
HINT: Divisibility rules and multiplication tables can
help you discover that a number that seems like a prime
number really isn’t.
Prime Numbers
However, even
never
numbers are
prime numbers
with one exception—
the number 2.
Prime Numbers
2 is a prime number,
because the only two factors
of 2
are 2
x 1 = 2.
Every other even number has 2 as a factor
too (that’s why no other even number is a
prime number).
Composite Numbers
Numbers
with more than two factors are
called composite
numbers. Numbers that
aren’t prime numbers are
composite numbers.
The special case of the number 1
The number 1 is
not a prime number and,
it is not a composite number.
Why? because, the number 1 only has
one factor, not two different factors.
1x1=1
The special case of the number 0.
Zero is another special number.
can not be a prime number because,
every number is a factor of 0.
0 x 1 does equal 0, but
0 x anything at all = 0
Zero
Zero is not a composite number either.
Only 0 and 1 are
neither prime
nor composite numbers.
All other whole
numbers are either
prime or composite
numbers.
Congratulations!
That’s how to tell a prime number from
a composite number.
Remember, if in doubt; with big
numbers, use divisibility rules.
With smaller products, use
multiplication tables.
And all even numbers, except 2, are
always composite.
QUESTIONS???