M3.1.6 For the adult
Prime factors, common factors and multiples
Can you build every whole number from prime numbers by multiplying?
What this chapter teaches
Every whole number bigger than 1 can be built from primes by multiplying, in only one way. A factor tree finds them. The highest common factor and lowest common multiple come from the same primes.
Three questions to ask
There is no one right wording. Listen for the idea.
- How would you split 60 until only primes are left?
- What is the biggest number that divides both 24 and 36?
- What is the smallest number that is in both the 6 and the 8 times tables?
After the chapter, the learner can
- Write 60 as a product of primes using a factor tree
- Find the highest common factor of 24 and 36
- Find the lowest common multiple of 6 and 8
What they copy into their notebook
Split a number into a factor pair, and keep splitting until every end is prime. 60 = 2 × 2 × 3 × 5. The HCF is the biggest shared factor. The LCM is the smallest shared multiple.