Maths · KS3 Y8 · Geometry & Measures

Angles in polygons

m16Free2:30Heddy Score 2 of 7, below the standard

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What you need to know

  • The interior angles of an n-sided polygon add to (n − 2) × 180°.
  • Exterior angles of any convex polygon add to 360°.
  • An interior and exterior angle at the same vertex add to 180°.

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
Also coversBest-buy comparisonsm95
Also coversDensity as a ratem97
Also coversCurrency conversionm100
Also coversInverse proportionm103
Also coversArea of a trapeziumm125
Also coversVolume of cylindersm140
Also coversVenn diagrams for probabilitym157
Also coversFrequency treesm159
Also coversArcs & sectorsmh14
Also coversFrequency polygonsmh19
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

Not enough students yet

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