For teaching and learning.

1. Objective
Be able to write a number as the
product of prime factors

2. Remember the prime numbers?
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ….
Here are the first ten prime numbers:
Why are they prime?
Each number has only two natural factors.
In every case the two factors are the
number itself and the number 1
The factors
of 2 are 1
and 2
The factors
of 3 are 1
and 3

3. Prime factor decomposition
Write the number 36 as the product of its
prime factors
36
Think of two
numbers
which
multiply
together to
give 36.
We could use
2 and 18
2 18 Now ask
yourself, “are
these prime
numbers?”
Is 2 a prime
number?
Yes. So we
can stop this
part of our
tree here.
Is 18 a prime
number?
No. So we
carry on
2
2
9
3 3
2
3 3
36 = 2 x 2 x 3 x 3
36 = 22
x 32

4. Prime factor decomposition
Write the number 28 as the product of its
prime factors
28
Think of two
numbers
which
multiply
together to
give 28.
We could use
7 and 4
7 4
Now ask
yourself, “are
these prime
numbers?”
Is 7 a prime
number?
Yes. So we
can stop this
part of our
tree here.
Is 4 a prime
number?No. So we
carry on
2
7
2
2
28 = 2 x 2 x 7
28 = 22
x 7
2

5. Now try some interactive questions
Click here to begin

6. Objective
Be able to write a number as the
product of prime factors

7. Objective
Be able to write a number as the
product of prime factors