JENECONKMaths Universe

Basic Probability

Ages 9–14

Difficulty adapts to you

Basic Probability

Probability measures likelihood from 0, meaning impossible, to 1, meaning certain. When all outcomes are equally likely, probability equals favourable outcomes divided by total possible outcomes.

Your goals

  • ✓You can understand and calculate the chance of events.
  • ✓You can use outcome, probability correctly.
  • ✓You can count favourable outcomes and all equally likely outcomes.

Words to know

outcome:
A possible result of an experiment.
probability:
A number from 0 to 1 showing how likely an event is.

Examples

  • 1For a fair coin, P(heads) = 1/2 = 0.5 = 50%.
  • 2For a fair six-sided die, P(rolling 6) = 1/6 ≈ 0.167, and P(even) = 3/6 = 1/2.

Check these

  • • Do not use the formula when outcomes are not equally likely.
  • • Keep every number, symbol, label, and unit in its correct place.
  • • Show enough working to check how you reached your answer.

Helpful habits

  • • Read the whole question before choosing what to do.
  • • Show one clear step at a time and check each step.
  • • If you are stuck, draw a model, try smaller numbers, or revisit the example.

Now try your own

Create your own basic probability example, solve it, and explain how you checked it.

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