Learning pack · IGCSE handout

Factors and Primes

What's in this pack: printable worksheet PDF, matching answers PDF (IGCSE / Secure–Stretch practice). Prime factorisation, HCF and LCM unlock fraction work, surds and index laws later.

Resources at the top · full summary · videos with short notes below.

🎒 Resources in this pack

Jump straight to the printable files, or scroll to the summary and videos.

Scaffolded Learning Sheet — attempt the worksheet, then use the Answers for a full written solution.

📝 Open Learning Sheet ✅ Open answers 🎬 More topic videos (6)📖 Full summary

Files: 21_factors_and_primes_handout.pdf · 21_factors_and_primes_handout_answers.pdf

Full topic summary

Prime factorisation, HCF and LCM unlock fraction work, surds and index laws later.

Key learning points

Prime numbers have exactly two distinct factors: 1 and themselves.
HCF: take lowest powers of shared primes; LCM: highest powers of all primes appearing.
Divisibility tests speed up factor trees.

Worked example 1 — HCF and LCM

HCF and LCM of $12$ and $18$ .

Working

\mathrm{HCF}=6,\ \mathrm{LCM}=36

Prime factors.

Worked example 2 — Prime test

Is $91$ prime?

Working

91=7\times13\Rightarrow\text{not prime}

Test primes up to $\sqrt{91}$ .

Worked example 3 — Product of primes

Express $84$ as a product of primes.

Working

2^2\times3\times7

Factor tree.

🎬 Topic videos

Math Antics - Integer Multiplication & Division
Math Antics · 10 min
Lower Secondary classroom-friendly explainer. Scaffold→stretch friendly; use with mixed-ability groups.
Comparing Decimal Numbers - Math Antics Extras
Math Antics · 5 min
Lower Secondary classroom-friendly explainer. Scaffold→stretch friendly; use with mixed-ability groups.
Division: Remainders vs. Decimals - Math Antics Extras
Math Antics · 4 min
Lower Secondary classroom-friendly explainer. Scaffold→stretch friendly; use with mixed-ability groups.
Introduction to Integers
Eddie Woo · 5 min
Lower Secondary classroom-friendly explainer. Scaffold→stretch friendly; use with mixed-ability groups.
Adding and Subtracting Integers (Applying operations to integers and visualising with Number line)
Eddie Woo · 12 min
Lower Secondary classroom-friendly explainer. Scaffold→stretch friendly; use with mixed-ability groups.
Subtracting with integer chips | Integers: Addition and subtraction | 7th grade | Khan Academy
Khan Academy · 6 min
Lower Secondary classroom-friendly explainer. Scaffold→stretch friendly; use with mixed-ability groups.

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Browse the hub Learning Packs & Summary, or open the compact Factors and Primes summary.