Basic Probability — Likelihood of an Event (Grades 6–7)
Probability measures how likely something is, as a fraction from 0 (impossible) to 1 (certain). For equally-likely outcomes, the probability of an event is the number of favorable outcomes divided by the total number of outcomes. Flipping a fair coin, P(heads) = 1 favorable / 2 total = 1/2.
Understanding basic probability
Probability measures how likely something is, as a fraction from 0 (impossible) to 1 (certain). For equally-likely outcomes, the probability of an event is the number of favorable outcomes divided by the total number of outcomes. Flipping a fair coin, P(heads) = 1 favorable / 2 total = 1/2.
Key Idea
Probability measures how likely something is, as a fraction from 0 (impossible) to 1 (certain). For equally-likely outcomes, the probability of an event is the number of favorable outcomes divided by the total number of outcomes. Flipping a fair coin, P(heads) = 1 favorable / 2 total = 1/2.
Seeing it in action
Worked example
A bag has 2 red and 4 blue marbles. P(red)?
Favorable (red) = 2; total = 2 + 4 = 6.
P(red) = 2/6 = 1/3.
Probability = favorable outcomes / total outcomes.
Try a few
A fair die: P(rolling a 3)?
5 red, 5 green: P(green)?
Spinner with 4 equal parts, 1 gold: P(gold)?
Spinner
A calm probability game for reading spinner sectors, fractions, complements, and comparisons.
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