Today is rung 9 of 9 on this topic
Factors, multiples and prime numbers
Can do: Lists factors of a number, knows what makes a number prime, and finds common multiples.
Why it matters
It's the vocabulary that fractions in Grade 5 and 6 are built from — simplifying and common denominators are both factor problems in disguise.
What it looks like when it's wobbly
Confuses factors with multiples, and calls 1 or 9 prime.
⏱️ Two-minute check
"List all the factors of 24. Is 9 prime? Why not?"
Solid looks like: 1, 2, 3, 4, 6, 8, 12, 24 — and 9 rejected because 3 × 3 works.
The full activity for this topic · 15 minutes
Rectangle Factor Hunt
- 1Give them 24 counters. Build every rectangle possible: 1×24, 2×12, 3×8, 4×6.
- 2Each rectangle's sides are a factor pair. Write them down in order.
- 3Try 7 counters. Only one rectangle exists — that's what prime means, made visible.
- 4Sort the numbers 1 to 20 into prime and composite using rectangles.
- 5Play factor bingo, or a fizz-buzz style game with multiples.
If it's too hard
Numbers under 20 with counters.
If it's too easy
Prime factorisation as a factor tree, which sets up simplifying fractions perfectly.
Say this
"How many different rectangles can you build with these? Each one gives you a factor pair."