Probability: Rock Paper Scissors

Australian curriculum number (ACMSP144; ACMSP145; ACMSP146)

This sequence builds students’ understanding of randomness. A random outcome is one for which all possibilities have an equal chance of being selected. Students recognise that games such as rock paper scissors are not truly random, as people’s decisions are influenced by whether they win or lose the previous game. Students see that playing the same game with cards or using a computer simulation produces a random result.

This sequence is for students who:

  • are familiar with calculating the probabilities of different events.
  • are ready to apply their understanding of fractions to express the probability of events occurring.


Lesson 1: How Random Is It?

Students determine their chances of winning the game rock paper scissors (RPS), then test their chances by playing against another player and in a simulation card or dice game. Students look at the psychological aspect of the game and recognise that there is a strategy to increasing their chance of winning.

Lesson 2: Which Is Better?

Students calculate the probabilities of winning the game rock paper scissors lizard Spock (RPSLS) and compare it to the chances of winning RPS. They decide which is the better game to play in different circumstances.


Last updated June 21 2020.