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Math Quiz III: Voting Systems and Proportions - Prof. John A. Paulos, Exams of Mathematics

Solutions to quiz iii for a math course, focusing on various voting systems and proportions. It includes calculations for determining nominees under plurality, runoff, borda count, and approval voting methods. Additionally, it covers insincere voting and power dynamics in stockholder meetings.

Typology: Exams

Pre 2010

Uploaded on 12/12/2009

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Math 0824/0924 Quiz III
Show all your work on the paper you hand in.
1. and 2. Imagine that there are 27 delegates (voters) to a political party's
convention at which four people Ann, Bob, Claire, and Dave have been nominated as
the party's candidates for governor. Assume the delegates' preference schedules are
as follows.
Number of Delegates 8 6 13
First Choice A B D
Second Choice B A C
Third Choice C C B
Fourth Choice D D A
1a). What nominee would win if the party uses the plurality method?
D with 13 first place votes.
1b). What nominee would win and by what margin if the party has a runoff between
top two candidates?
A wins. A would beat D in a runoff, 14 to 13.
1c.) What nominee would win if the party uses a Borda count which assigns 4, 3, 2,
and 1 point(s) for a first, second, third, and fourth choice, respectively. Show
calculations.
A: 8*4 + 6*3 + 13*1 = 63.
B: 8*3 + 6*4 + 13*2 = 74
C: 8*2 + 6*2 + 13*3 = 67
D: 8*1 + 6*1 + 13*4 = 66.
So B wins in a Borda Count.
2a). If the candidates in the big bold font are approved of by the number of delegates
indicated, what nominee wins and by what margin if approval voting is used?
A-14; B-6; C-19; D-13. C wins.
2b). What if the 6 voters who approve of B, A, and C decide that they don't approve
of C after all. Now who wins by approval voting?
C loses 6 approvals, so C has only 13, the same as D, so C and D are tied, and A wins
with 14 approvals.
2c.) Who, if anyone, is the Condorcet winner?
B versus A, B wins; B versus C, B wins; B versus D, B wins, so B is the Condorcet
winner.
3a.) You prefer Mexican to Italian to Chinese food, but your two friends hate
Mexican food. One prefers Italian, the other Chinese. You're all deciding where to
eat. How might you be tempted to tell your friends about your preferences, and
what does this have to do with insincere or strategic voting?
You vote insincerely and pretend you prefer Italian to Mexican to Chinese. By doing
so you can at least get your second choice of Italian instead of your last choice of
Chinese.
3b.) If you're is 6 blocks west and 5 blocks south of the restaurant you've decided
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Math 0824/0924 Quiz III Show all your work on the paper you hand in.

  1. and 2. Imagine that there are 27 delegates (voters) to a political party's convention at which four people Ann, Bob, Claire, and Dave have been nominated as the party's candidates for governor. Assume the delegates' preference schedules are as follows. Number of Delegates 8 6 13 First Choice A B D Second Choice B A C Third Choice C C B Fourth Choice D D A 1a). What nominee would win if the party uses the plurality method? D with 13 first place votes. 1b). What nominee would win and by what margin if the party has a runoff between top two candidates? A wins. A would beat D in a runoff, 14 to 13. 1c.) What nominee would win if the party uses a Borda count which assigns 4, 3, 2, and 1 point(s) for a first, second, third, and fourth choice, respectively. Show calculations. A: 84 + 63 + 131 = 63. B: 83 + 64 + 132 = 74 C: 82 + 62 + 133 = 67 D: 81 + 61 + 134 = 66. So B wins in a Borda Count. 2a). If the candidates in the big bold font are approved of by the number of delegates indicated, what nominee wins and by what margin if approval voting is used? A-14; B-6; C-19; D-13. C wins. 2b). What if the 6 voters who approve of B, A, and C decide that they don't approve of C after all. Now who wins by approval voting? C loses 6 approvals, so C has only 13, the same as D, so C and D are tied, and A wins with 14 approvals. 2c.) Who, if anyone, is the Condorcet winner? B versus A, B wins; B versus C, B wins; B versus D, B wins, so B is the Condorcet winner. 3a.) You prefer Mexican to Italian to Chinese food, but your two friends hate Mexican food. One prefers Italian, the other Chinese. You're all deciding where to eat. How might you be tempted to tell your friends about your preferences, and what does this have to do with insincere or strategic voting? You vote insincerely and pretend you prefer Italian to Mexican to Chinese. By doing so you can at least get your second choice of Italian instead of your last choice of Chinese. 3b.) If you're is 6 blocks west and 5 blocks south of the restaurant you've decided

upon, how many ways are there to get to it? The number of ways of choosing 5 from 11, which equals the number of ways of choosing 6 from 11, which is 1110987/54321 or 462. 5a.) In a certain company there are four stockholders, A,B,C, and D. A owns 30% of the stock, B owns 28%, C 22%, and D the remaining 20% of the stock. If 51% of the vote is needed to pass a measure, explain intuitively (no diagrams for this question) why A has more power than the others. A has more power than the others since he can get his way if either one of B or C to agree with him, whereas the the other 3 get their way without A only if they all band together. 5b.) Explain (again no diagram) why in a different company where A has 27%, B has 26%, C has 25%, and D has 22% of the vote, then stockholder D has no power at all. There is no situation in which D's vote makes a difference one way or the other. If at least two of A, B and C decide on something, then it passes or fails. 6a.) Using the percentages from the previous problem 5a.), construct the appropriate table of Y's and N's and calculate the total percentages in each case and whether the measure passes or not. 6b.) Circle the crucial votes to determine the relative powers of the four stockholders. The usual array of 16 lines. Do the Banshaf circlings to get 10, 6, 6, and 2 for A, B, C, and D, respectively.

  1. The dimensions of a model car (length, width, height) are 1/7 of the dimensions of a real car. The model is made of the same material as the real one. 7a.) If the model is 2 feet long, how long is the real one? It's 2 x 7 = 14 feet long. 7b.) If if 2 gallons of paint is needed to paint the model, how much is needed to paint the real one? Area is the relevant dimension, so 2 x 72 = 98 gallons of paint. 7c.) If the model weighs 24 pounds, how much does the real car weigh? Weight and volume vary together, the real car weighs 24 x 73 = 8232 pounds. 8a.) A swimming pool is 20 feet by 15 feet and 5 feet deep. What is its volume in cubic feet? What is its volume in cubic inches? The volume in cubic feet is 20 x 15 x 5 = 1,500 ft3. In cubic inches it's 1,500 x 123 = 2,592,000 in3. 8b.) Consider a larger pool whose dimensions are 1.5 times the dimensions of the original pool. If the original pool holds 2 million jelly beans, how many does the larger pool hold? Volume again, so the bigger pool holds 2 million x 1.53 jelly beans = 2,000,000 x 3.375 = 6,750,000 jelly beans.
  2. What is the story behind the Prisoner's Dilemma and say why it is important in many different domains. Draw the appropriate diagram.