How do you decide what a group wants? The usual answer is to vote. But if there are more than 2 contenders there are always paradoxes, the most notorious being the “spoiler” effect. Voting for what you really want can take votes away from what you would find acceptable, leading to the victory of what you thoroughly dislike. Instant run-off Voting is one of a number of ranked-choice voting systems that eliminates the spoiler effect.
The activity consists of voting for your favorite dessert. When I first tried this activity the class consisted of a handful of parents and a large number of kids from second grade through high school. The kids named their favorite desserts (about a dozen of them) which I listed on the board. I then told them my favorite dessert was broccoli. (I had arranged with the few adults in the class that they would vote for broccoli.) Broccoli won with a small minority support because the votes for sweet desserts were spread across the whole spectrum. The students were outraged, especially when I argued that this proved that broccoli was the class’s favorite dessert!
We then voted again, this time ranking the desserts in order of preference. The rule is that an actual majority of the votes is required to win. If the balloting fails to produce a majority for one candidate, the candidate with the smallest number of votes is eliminated and the votes for that candidate are redistributed according to the most favored surviving candidate. This process is repeated until there is an actual majority. (Chocolate mousse won, after several eliminations.)
[Epilogue: When the gardening class brought in their harvest I was brought gifts of broccoli by numerous students, who insisted I take it home and have it for dessert. Fortunately I actually do like broccoli!]