Factors, Highest Common Factors & Primes

Task goals

• List all the factors of a whole number systematically in factor pairs so none are missed.
• Decide whether a number is prime or composite, knowing that $1$ is not prime and $2$ is the only even prime.
• List the factors of two numbers, compare the lists to find their common factors, and identify the highest common factor (HCF).
• Check whether a stated factor, common factor, or HCF is correct, and explain any error.
• Use a factor tree to write a whole number as a product of prime factors, in both repeated-product and index form.
• Solve a reasoning problem that uses factor counts, such as finding a number in a given range with an exact number of factors.