Maths · GCSE · Probability

Combined events

Combined eventsFree5:47Heddy Score 3 of 7, below the standard

What you need to know

  • The sample space for one dice is {1, 2, 3, 4, 5, 6}, and probability = favourable outcomes ÷ total outcomes.
  • 'A and B' means outcomes in both events, and 'A or B' means outcomes in either.
  • An event and its complement ('not A') together cover every outcome, so their probabilities add to 1.
  • So P(not A) = 1 − P(A): if P(red) = 0.35, then P(not red) = 0.65.

In this clip

0:00–5:45Probabilities sum to 1
Also coversCombined events
Heddy Score3/7, Below the standard
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  • 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 · passed. 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
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On YouTube

943K views · 11.4K likes · The Organic Chemistry Tutor 11.1M subscribers

As reported by YouTube on 2026-11-03. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

Shows from a simple dice example why P(A) and P(not A) must add up to 1, then uses that to find a missing probability.

The Organic Chemistry Tutor on YouTubechecked 2026-10-22

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