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11.1 Voting Methods

Plurality, runoff, ranked choice, Borda count, pairwise Condorcet comparison, and approval ballots, each applied to the same preference schedule.

Contemporary Mathematics, 11.1 Voting Methods

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12 exercises

11.1 Exercise 1

Refer back to the table. Did any single candidate secure the majority of popular votes?

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11.1 Exercise 3

Refer again to the table. In the 2000 U.S. presidential election, which candidate had a plurality of popular votes?

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11.1 Exercise 5

A condominium association elects a new president every two years by a two-round system of voting. If none of the candidates receive a majority, the association charter states that the top two candidates will be eligible to participate in a runoff election. In a particular year, five residents were nominated. The results of the first round are given in the table below.

  1. Is there a winner based on…
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11.1 Exercise 7

The five members of the Chionilis family—Annette, Rene, Seema, Titus, and Galen—have decided to get takeout for dinner. They are trying to decide on a restaurant. The options are Rainbow China, Dough Boys Pizza, Taco City, or Caribbean Flavor. They will use majority election with runoffs where the restaurant with the fewest votes is eliminated in each round. The preferences of each family member a…

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11.1 Exercise 9

Refer to the table below containing voters’ preference rankings to answer the following questions.

  1. How many voters ranked the options in the following order: Option A in fourth place, Option B in second place, Option C in first place, and Option D in third place?
  2. How many ballots in total were collected?
  3. How many voters indicated that Option C was their first choice?
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11.1 Exercise 11

Let’s review the kindergarten class color preferences again, and this time determine which color would be selected based on these results using the ranked-choice method.

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11.1 Exercise 13

Let’s review the ballots from the kindergarten class again, as shown in the table below. This time, let’s determine the Borda score received by the color purple.

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11.1 Exercise 15

Use the table below, which displays a sample preference summary, to answer the questions that follow.

  1. Use the ranked-choice voting method to determine the winner of the election.
  2. Use the Borda count method to determine the winner of the election.
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11.1 Exercise 21

  1. Suppose there is an election with five candidates—A, B, C, D, and E—and that Candidate C is a Condorcet candidate. How many points did Candidate C win?
  2. What is the greatest number of points that any one of the other candidates could win?
  3. Is it possible for Candidate C to lose or tie?

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11.1 Exercise 25

The eight members of the Chionilis family—Annette, Rene, Seema, Titus, Galen, Elena, Max and Demitri—have another decision to make. Approval voting worked out nicely the last time. They are going to use it again, but this time, Annette, Rene, Seema, and Galen are feeling a little indecisive. They can't narrow their choice down to two. They will approve their three top choices, but the other family…

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11.1 Exercise 27

Because the vote counts for George W. Bush and Al Gore differed by only 537 votes, many Democrats blamed Ralph Nader and the Green Party for their loss. Let’s consider how the election results might have differed if the approval voting method had been used.

Use the table and the following assumptions to extrapolate the results of an approval method election:

  1. 100 percent of Pat Buchanan supporters…
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11.1 Exercise 29

In the future, humans have explored distant solar systems and found three habitable planets which could be colonized. Since it will take all available resources to colonize one planet, humans must agree on the planet. Planet A has the most comfortable climate and most plentiful resources, but it is the farthest from Earth making travel to the planet a challenge. Planet B is half the distance but w…

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Adapted from Contemporary Mathematics © 2023 Rice University. Licensed under CC BY 4.0. Source: Contemporary Mathematics. Imported at revision fa7c1a1.