Maths · KS3 Y9 · Number

HCF & LCM by prime factors

m54Free2:43Heddy Score 2 of 7, below the standard

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What you need to know

Write each number as a product of primes.
The HCF uses the primes the numbers share.
The LCM uses every prime needed by either number.
A Venn diagram of prime factors makes both easy to read off.

In this clip

1:54–2:34Prime factorisationm26

2:34–5:17HCF & LCM by prime factorsm54

5:17–6:20Inequalities on a graphgcse-math-a22b

7:34–11:09Reverse percentagesm52

11:09–12:42Simple interest and money mathsgcse-math-r9b

12:42–16:41Compound interestmh12

20:00–21:40Standard form: large numbersm46

21:40–22:25Laws of indicesm41

22:25–23:20Fractional indicesmh6

23:20–25:05The product rule for countinggcse-math-n5b

25:05–27:03Error intervalsmh5

31:32–33:10Expanding a single bracketm61

33:10–34:33Quadratic expressionsmh1

34:33–36:15Factorising into a bracketm66

39:25–41:08Unknowns on both sidesm69

41:08–42:36Rearranging simple formulaem71

43:30–49:39Simultaneous equationsm19

57:49–60:53nth term of linear sequencesm70

63:32–67:20Graphs of quadraticsm85

71:34–75:27Ratio notationm7

85:58–89:49Speed, distance, timem96

91:17–93:20Pythagoras: the hypotenusem136

93:20–96:09Angles in parallel linesm123

96:09–98:39Angles in polygonsm16

109:47–111:50Bearingsm134

115:32–117:34Enlarging shapesm130

125:20–127:05Scatter graphs & correlationm20

135:10–139:29Tree diagramsmh17

141:55–145:36Trigonometry first stepsmh2

145:36–147:47Trigonometry: finding anglesmh16

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Heddy Score2/7, Below the standard

Trusted source · passed. The creator's own upload, live and playable here.
On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
Spec-true · not judged yet. Accurate, and right for the current UK specification.
Focused · passed. One idea, short enough to watch in one go.
Accessible · not judged yet. Good captions, clear sound and pictures.
Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.

★ passed · ☆ pending · ✕ failed

Our students

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Our own students' answers. These are what move ★7 Proven.

How the Heddy Score works

Why we picked it

Long crossover revision video covering the topics shared by Foundation and Higher; best used chapter by chapter by Year 10–11 students aiming for grade 5.

The GCSE Maths Tutor on YouTubechecked 2026-10-16