| Magazine | Supplements | Subscribe | Jobs | Submit an article | Advertise | Academy |
|
|
||||||
|
|
||||||
|
Now you can search for articles in back issues of Contingencies from July/August 2000 to the present. Simply type in subject words, author's name, or article title in the box at right and click Search. |
|
Tax Season Hiringby Yan Fridman THIS ISSUE’S PUZZLELet’s finish the year with a relatively simple math puzzle. It was offered a long time ago at a math competition. It’s November, and an online tax preparation firm, FileWithUs.com, starts to recruit CPAs for the next year as the tax filing season approaches rapidly. The company isn’t large, and Mr. Rouge, the manager, plans to finish the hiring process by the end of November. Mr. Rouge is known to be a very peculiar man, and so is his hiring pattern. During the first day, he plans to fill one position and then one-seventeenth of the remaining positions. (Mr. Rouge knows in advance the number of openings.) During the second day, he will hire two more people and then fill one-seventeenth of the remaining positions. The pattern continues, and during the final day of hiring, he will employ n people and then fill one-seventeenth of the remaining positions. Please answer the following questions: 1. How many business days will it take Mr. Rouge to complete
hiring? PREVIOUS ISSUE’S PUZZLEANSWERS TO BLUELAND SOCCER TOURNAMENT PUZZLE 1. The SolutionMiners and Bankers are able to create some inequity in the chances to win the tournament solely due to the asymmetrical scoring system; a combination of a win and a loss is better than two ties. Why in this situation these two teams would tie is unknown. Perhaps in the real world it would never happen. However, it makes an interesting math puzzle. The actual solution could be quite long, so I will try to squeeze the main points within the limits of the puzzles page. 1. There are 243 different scoring combinations. They can be split based on the number of ties (excluding the tie between the Miners and the Bankers) as follows: If the number of ties is t, the number of possible combinations is 2. This is very similar to the first case. Inequities arise when t = 3 or 4, where t is the total number of ties. Expectation of making finals decreases to 18²⁄³ (compared to 20) out of 40 (t=3) and 4 (compared to 5) out of 10 (t=4). Again, the cases are left as an exercise. (Hint: Army will be at a disadvantage if it ties all three games; this will be offset against the cases in which Police ties all three games.) Total probability of the Police team making the final game is 3. Police wins the championship with 50 percent probability
if it advances to the final game with certainty. The probability of the Police team’s making the finals equals By solving the integral equation, you find q > 1, which is impossible.
A more interesting question: What probability q triggers the expectation of the Police advancing to the final game to be equal to one-half? The same logic applies as we need to solve the equation.0. 4. The old scoring system was fair in that it prevents inequities from occur- ring. Therefore, the probability of Army’s or Police’s winning the group stage is 50 percent, regardless of the Miners-Bankers strategy. Chess Puzzle. White to move and mate in three. Initial position: White—Ka7, Rf1, Ba2, Bc5, pawns b4, c6, e2. Black—Ke4, pawns c7, d7, e5. CHESS PUZZLE SOLUTION. Case A: 1. Bg8! dxc; 2. Rf7 Kd5; 3. Rf4# Case B: 1. Bg8! d6; 2. Bg1 d5; 3. Bh7# SOLVER LISTSDue to an administrative deadline, names of only those people who submitted cor- rect solutions by Sept. 30, 2005, are shown on the lists. Soccer Puzzle: Bob Byrne, Mark Evans, Chi Kwok, Lee Michelson, Brian Miller, Al Spooner, Jeanette Woodhall Chess Puzzle: Mike Crooks, Lee Michelson
|
November/December 2005Enterprise Risk Management for Insurers: Actuarial Theory in Practice Operational Risk: The New Frontier Social Security Reform: What's the Best Fix? Inside Track: Commentary: Policy Briefing: Workshop: Tradecraft: Puzzles: Endpaper:
|
|
|
||
PDF version
or 5, inequities are not explored and the probability of making the final match for any team is 50 percent. However, if t = 2 or 3, then the Police team gets an advantage in just a few cases and the expectation of making finals increases to 42 2/3 (compared to 40) out of 80 (t=2) and 22 (compared to 20) out of 40 (t=3). The cases could be counted with some work and are left to the readers as an exercise. (Hint: Police will be at an advantage, for example, if one of the cheating teams ties all games.) Total probability
of the Police team making the final game is
to zero, you can find the answer.
to zero, you can find the answer.
. Since p is assumed to be uniformly distributed on [0, 1], the following must take place:1
This equation solves for q = 8/13.
THIS ISSUE’S CHESS PUZZLE