Maths GCSEPrime Factorisation

Objectives:To express a whole number as a sum of its prime factorsTo express a whole number as the product of powers of its prime factors

Starter Activity

Work out the .....

First 10 prime numbers

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

Express 12 as a sum (product) of its prime factors …

Which is correct, a, b, or c?

a) 12 = 2 x 6b) 12 = 3 x 4c) 12 = 2 x 2 x 3

Silly Prime Rhyme

Start with low prime numbers if you canCircle the prime numbers, now that’s a good

plan!Keep dividing the number until you have only

primesMaybe 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

Step 2:The number 36 is then written as the sum (product) of primes like this: 36 = 2 x 2 x 3 x 3and / or36 = 2²x 3²

Step 1:A factor tree to show the prime factors of the number 36

Example

36

÷2

18

9

÷2

÷3 ÷3