Finding prime factors
primeA number that only has two factors - itself and one. factors are factorA factor is a number which divides exactly into another number. 1 is a factor of every number and every number is a factor of itself. A number can have several factors. Example: 1, 2, 5 and 10 are the factors of 10. of a number that are, themselves, prime numbers.
Sometimes you might be asked to write a number as the productThe answer when two or more numbers are multiplied together, eg the product of 4 and 15 is 60. of its prime factors.
There are many methods to find the prime factors of a number, but one of the most common is to use a prime factor tree:
- Start the factor tree using any pair of factors (two numbers that multiply together to make your number).
- If one of these factors is prime, that branch ends.
- If a factor isn't prime, divide it into a factor pair.
- The branches continue to expand until all the factors are prime numbers.
- The final answer is the list of all the prime numbers displayed at the end of these branches.
Example:
Write 24 as the product of its prime factors.
Image caption, Write 24 as the product of its prime factors
You could choose any factor pair to start.
Image caption, Write 24 as the product of its prime factors
Find the factor pair for one of the new factors.
Image caption, Write 24 as the product of its prime factors
Find the remaining factor pairs in the same way.
Image caption, Write 24 as the product of its prime factors
24 written as the product of its prime factors is 2 × 2 × 2 × 3.
1 of 4