Maths GCSE topic - prime factorisation

1. Maths GCSE
Prime Factorisation
Objectives:
To express a whole number as a
sum of its prime factors
To express a whole number as
the product of powers of its
prime factors

2. Starter Activity
Work out the .....
First 10 prime numbers

3. Learning Objectives:
•To express a whole number as a sum
of its prime factors
•To express a whole number as the
product of powers of its prime
factors
Success Criteria:
•You can complete factor trees when
given the branches
•You can independently draw factor
trees for 3 digit numbers

4. Express 12 as a sum (product) of its prime
factors …
Which is correct, a, b, or c?
a) 12 = 2 x 6
b) 12 = 3 x 4
c) 12 = 2 x 2 x 3

5. Silly Prime Rhyme
Start with low prime numbers if you can
Circle the prime numbers, now that’s a good plan!
Keep dividing the number until you have only primes
Maybe try to remember this silly prime rhyme!
Once you’ve drawn your ‘prime factor tree’
Write the primes as a sum, like 2 x 2 x 3

6. Step 2:
The number 36 is then
written as the sum (product) of primes like this:
36 = 2 x 2 x 3 x 3
and / or
36 = 2²x 3²
Step 1:
A factor tree to show the prime factors
of the number 36
Example
36
÷2
18
9
÷2
÷3 ÷3