Probability as a Fraction
Describe the probability of simple equally-likely outcomes using unit fractions: the probability of rolling a 6 on a fair die is 1/6, flipping heads is 1/2, picking one specific colour from three equally represented colours is 1/3; place these fractional probabilities on a 0-to-1 probability scale
What a learner can do afterwards
- State that the probability of rolling a 6 on a fair die is 1/6 and explain why
- Express the probability of picking a red card from a standard deck as 26/52 or 1/2
- Write the probability of a simple event as a fraction: favourable outcomes over total outcomes
The lesson
Probability tells you how likely something is to happen. You can write it as a fraction: the number of outcomes you want, over the total number of equally likely outcomes.
Flip a fair coin. There are 2 equally likely outcomes: heads or tails. Heads is 1 of them, so the probability of heads is 1/2.
A bag has 3 balls, one red, one blue, one green, all equally likely to be picked. Picking the red ball is 1 outcome out of 3, so the probability is 1/3.
To write any simple probability as a fraction, put the outcomes you want on top and all the equally likely outcomes on the bottom. A probability of 0 means impossible, and a probability of 1 means certain, so fractions like 1/6, 1/3, and 1/2 sit somewhere in between.
Probability as a fraction is favourable outcomes over total outcomes, sitting somewhere between 0 (impossible) and 1 (certain).
Watch it
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.