Probability as a Fraction
Describe the probability of simple equally likely outcomes with fractions, including unit fractions such as 1/6, 1/2, and 1/3, and place these probabilities on a 0-to-1 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
- Place simple probabilities such as 0, 1/4, 1/2 and 1 on a 0-to-1 scale, where 0 means impossible and 1 means certain
1 · Read
Probability tells how likely an event is. When all outcomes are equally likely, write probability as favourable outcomes over total outcomes. The favourable count is the top number, called the numerator. The total count is the bottom number, called the denominator.
A spinner has 8 equal sections, and 1 of them has a star. There are 8 equally likely outcomes, and the star is 1 of them, so the probability of landing on the star is 1/8.
A bag has 7 equally likely counters: 3 yellow and 4 green. Yellow is 3 out of 7, so its probability is 3/7. A standard deck has 52 cards in four suits of 13. Hearts are one suit, so the probability of a heart is 13/52. Hearts and diamonds are the two red suits, so half the deck is red.
On a probability scale, 0 means impossible and 1 means certain. Fractions between them show chances between those ends. A fraction closer to 0 is less likely. A fraction closer to 1 is more likely. To compare two fractions, give them the same bottom number. 1/3 is the same as 2/6, because each third splits into 2 sixths. So 2/6 sits nearer to 1 than 1/6 does.
Probability as a fraction is favourable outcomes over total outcomes, sitting somewhere between 0 (impossible) and 1 (certain).
Linked YouTube videos: 'Calculating Probability as a Fraction' by EasyTeaching and 'Basic Probability | Is It Equal, Likely, Unlikely, Certain, or Impossible?' by Turtlediary; the videos belong to their channels, and only the link records were curated for os-taxonomy. The three readings, the nine extra practice questions and the six flashcards were written for os-taxonomy.
2 · Watch
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