Year 10 Foundation · Probability
Work out the chance of a single outcome
Definition
Probability measures how likely an event is, on a scale from 0 (impossible) to 1 (certain). It is the number of ways the event can happen divided by the total number of equally likely outcomes.
Why Do I Have to Learn This?
Probability measures how likely something is, from coin flips to weather forecasts. It helps you judge risk and chance sensibly.
Key Rules:
- 1. Probability = favourable outcomes ÷ total outcomes.
- 2. All the probabilities of an event add up to 1.
- 3. P(not happening) = 1 − P(happening).
Remember:
- •A probability can never be more than 1 or less than 0.
- •"Even chance" means a probability of ½, or 0.5.
- •Past results do not change a fair future event, a coin has no memory.
Event
Something that might happen, made up of one or more outcomes.
“Rolling an even number” is an event made of the outcomes 2, 4 and 6.
Animated Example:
Free Work out the chance of a single outcome Worksheet
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Before this: Sets and probability (Year 9) · Next: Set notation and Venn diagrams (Year 11 Foundation)
Let’s Practise the Concept
Step 1 of 3
Put them in order
Tap the numbers from smallest to largest.
In order so far: nothing yet