|
A prime number has only two different factors, 1 and itself.
So, 13 is a prime number since it has only two different factors, 1 and 13.
 -
Composite Numbers
- A composite number is a number that has more than two factors.
-
 - So, 10 is a composite number as it has more than two factors.
Note:
1 is considered neither a prime number nor a composite number as it has 1
factor only. A prime number has 2 different factors.
Example 19
State which of the following numbers are a prime:
a. 6
b. 19
Solution:
Prime Factors
Prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, …
A prime factor is a factor of a number that is also a prime
number.
To express a whole number as a product of prime factors,
try prime numbers in order of their magnitude. That is, first try to
find out whether 2 is a factor of the given whole number or not. If 2
is a factor of the whole number, it will divide into it exactly and we can
write the whole number as the product of 2 and another number. If 2 is
a prime, try 2 again to see if we can further write the whole number as a
product involving two 2s. If not, try the next prime, 3, and so
on. Stop when the number has been expressed as the product of prime
numbers.
Example 20
Express 90 as a product of prime numbers.
Solution:
Alternative solution:
We can use a factor tree to express 90 as a product of prime numbers.
Example 21
Express 200 as a product of prime numbers.
Solution:
Key Terms
prime number, composite number, prime
factor, product of prime factors, factor
tree
|
