Math · Stage 5
Primes, prime factorisation, HCF and LCM
Split any number into its prime building blocks, then use those primes to find the highest common factor and lowest common multiple of a pair.
✦ Math📘 Stage 5 · S5⏱ ~12 min🧒 Ages 9–10★ Free to start
I can find prime factors, the HCF and the LCM.
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Kavi's Prime Factory 🏭
Kavi lines the numbers up at his Prime Factory. "Some numbers can't be split any further — the primes 2, 3, 5, 7… are the building blocks of every other number," he hoots. "Once I know a number's primes, I can snap any pair together to find their HCF and LCM ⚡."
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What your child will learn
1Prime or composite?A prime number has exactly two factors — 1 and itself (2, 3, 5, 7, 11…). A composite number has more than two factors, so it can be split into smaller whole-number pieces (4 = 2×2, 6 = 2×3). Tap Prime or Composite for each number.
2Multiples and the LCMA multiple of a number is any number in its times-table — the multiples of 4 are 4, 8, 12, 16… The LCM (Lowest Common Multiple) of two numbers is the smallest number that appears in both times-tables. The lit numbers below are the multiples of 4.
3HCF vs LCMTwo jobs, two different answers — and prime factors do both. For the HCF, multiply the primes the two numbers share; for the LCM, multiply every prime, taking the most of each. Tap each card.
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A peek inside
Write 36 as a product of its prime factors.
36 → 4 × 9 → (2 × 2) × (3 × 3)
Try this at home: Is 23 prime or composite? __
Ready to play and learn?
Start the free interactive lesson, or print the handout for screen-free play.
Part of Math · Stage 5 · S5 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.