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Nonplussed!: Mathematical Proof of Implausible Ideas [NOOK Book]

Overview

Math—the application of reasonable logic to reasonable assumptions—usually produces reasonable results. But sometimes math generates astonishing paradoxes—conclusions that seem completely unreasonable or just plain impossible but that are nevertheless demonstrably true. Did you know that a losing sports team can become a winning one by adding worse players than its opponents? Or that the thirteenth of the month is more likely to be a Friday than any other day? Or that cones can roll unaided uphill? In ...

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Nonplussed!: Mathematical Proof of Implausible Ideas

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Overview

Math—the application of reasonable logic to reasonable assumptions—usually produces reasonable results. But sometimes math generates astonishing paradoxes—conclusions that seem completely unreasonable or just plain impossible but that are nevertheless demonstrably true. Did you know that a losing sports team can become a winning one by adding worse players than its opponents? Or that the thirteenth of the month is more likely to be a Friday than any other day? Or that cones can roll unaided uphill? In Nonplussed!—a delightfully eclectic collection of paradoxes from many different areas of math—popular-math writer Julian Havil reveals the math that shows the truth of these and many other unbelievable ideas. Nonplussed! pays special attention to problems from probability and statistics, areas where intuition can easily be wrong. These problems include the vagaries of tennis scoring, what can be deduced from tossing a needle, and disadvantageous games that form winning combinations. Other chapters address everything from the historically important Torricelli's Trumpet to the mind-warping implications of objects that live on high dimensions. Readers learn about the colorful history and people associated with many of these problems in addition to their mathematical proofs. Nonplussed! will appeal to anyone with a calculus background who enjoys popular math books or puzzles.

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Editorial Reviews

Plus Magazine
A review of a book as good as this must either repeat the positive adjectives other reviewers have used, or require a very large thesaurus. Since I find myself in complete agreement with all of the following words from other reviews, I will repeat them immediately: marvelous, crystal-clear, great, amazing, stimulating, delightful, fascinating, strong, surprising, classic, interesting, eclectic, insightful, magnificent. That one book could encourage such gushing praise seems as unlikely as one book being able to cram in a great variety and depth of mathematical problems, colourful historical anecdotes, significant nods to ethno-mathematics, difficult but well-explained proofs, clear and engaging prose and beautiful diagrams. Yet Havil's book succeeds on all accounts...The brilliant writing, the wonderful problems, the weaving together of past and future, games and discovery, and world number cultures will have you returning to this ageless book time and again.
— Phil Wilson
Times Higher Education
This is an exciting book. It should be in every sixth-form and college library. It would be the right gift for mathematicians and anyone who uses mathematics—economists, business analysts and many others—and indeed for anyone who would claim to be educated.
— Peter M. Neumann
Times Higher Education Supplement
Nonplussed! is a collection of lovely paradoxes: facts that are provable logically but are nevertheless seriously counterintuitive...It is an exciting book. It should be in every...college library. It would even be the right gift for mathematicians and anyone who uses mathematics—economists, business analysts and many others—and indeed for anyone who would claim to be educated.
— Peter M. Neumann
London Mathematical Society Newsletter
This is a splendid collection of articles, inspired by Martin Gardner's writings. Old conundrums are given new twists and applications, newer perplexing ideas are described with panache. The forthcoming companion book has a high standard to maintain.
— John Haigh
MAA Review
It is therefore recommended that Julian Havil's headmaster award him further sabbatical leave for the purpose of producing a sequel to this welcome addition to the mathematical literature.
— Peter Ruane
Choice
This fascinating expedition by Havil through some engaging and often surprising mathematical and statistical oddities is more demanding than the usual 'popular math book' it is billed...All topics are covered by an always carefully crafted mathematical exposition, not leaving out necessary preliminaries and providing rigorous proofs.
— J. Mayer
Mathematics Teacher
The book is perfect for independent or group study for students in advanced high school mathematics classes or university-level undergraduate mathematics classes. Selected chapters are suitable for discussion during professional development sessions aimed at engaging mathematics teachers in rigorous mathematics investigations and discussions.
— Anne Papakonstantinou
Mathematics Today
This is a fun book containing many diverse problems that I had not seen before but it also stimulates some genuinely interesting mathematical thought. Above all, this book highlights the 'frailty of the intuition we routinely use to guide us through our everyday lives' and that, in my mind, is no bad thing.
— Nathan Green
Mathematical Reviews
This book discusses such problems in a generally accessible way, but it does not shy away from using rigorous mathematical arguments to explain them. . . . Some of these topics are quite familiar, but even so I found the discussions clear and often learned some new and quite surprising tidbits.
— Stan Wagon
Kybernetes
Those that spend their working lives avoiding mathematics by approaching their problems in all sorts of different ways will benefit from looking at this text, even if it involves following through but one single problem and its mathematical solution.
— C.J.H. Mann
Mathematics in School
Havil has an excellent mix of an interesting history of each topic and clear and lucid solutions to the problems. . . . Havil's strength is the historical background he gives to each topic and his style of writing which is so easy to read. . . . An interesting and challenging book well worth reading.
— John Sykes
Mathematical Intelligencer
I recommend the book to everyone interested in entertaining mathematics.
— Christina Birkenhake
Zentralblatt MATH

This lovely book will attract the attention of readers who are interested in recreational mathematics like mathematical puzzles and paradoxes.
— Yuri V. Rogovchenko
Times Higher Education Supplement - Peter M. Neumann
Nonplussed! is a collection of lovely paradoxes: facts that are provable logically but are nevertheless seriously counterintuitive...It is an exciting book. It should be in every...college library. It would even be the right gift for mathematicians and anyone who uses mathematics—economists, business analysts and many others—and indeed for anyone who would claim to be educated.
London Mathematical Society Newsletter - John Haigh
This is a splendid collection of articles, inspired by Martin Gardner's writings. Old conundrums are given new twists and applications, newer perplexing ideas are described with panache. The forthcoming companion book has a high standard to maintain.
MAA Review - Peter Ruane
It is therefore recommended that Julian Havil's headmaster award him further sabbatical leave for the purpose of producing a sequel to this welcome addition to the mathematical literature.
Plus Magazine - Phil Wilson
A review of a book as good as this must either repeat the positive adjectives other reviewers have used, or require a very large thesaurus. Since I find myself in complete agreement with all of the following words from other reviews, I will repeat them immediately: marvelous, crystal-clear, great, amazing, stimulating, delightful, fascinating, strong, surprising, classic, interesting, eclectic, insightful, magnificent. That one book could encourage such gushing praise seems as unlikely as one book being able to cram in a great variety and depth of mathematical problems, colourful historical anecdotes, significant nods to ethno-mathematics, difficult but well-explained proofs, clear and engaging prose and beautiful diagrams. Yet Havils book succeeds on all accounts...The brilliant writing, the wonderful problems, the weaving together of past and future, games and discovery, and world number cultures will have you returning to this ageless book time and again.
Choice - J. Mayer
This fascinating expedition by Havil through some engaging and often surprising mathematical and statistical oddities is more demanding than the usual 'popular math book' it is billed...All topics are covered by an always carefully crafted mathematical exposition, not leaving out necessary preliminaries and providing rigorous proofs.
Mathematics Teacher - Paul Kelley
Even many high school students without a calculus background will benefit from the problems contained in the book. . . . The book contains a little algebra, some geometry, and a great deal of probability. It could serve as recreational reading for teachers as well as for student use in a probability course or courses following algebra 2. Mathematics clubs and teams would also find Nonplussed! useful.
Mathematics Today - Nathan Green
This is a fun book containing many diverse problems that I had not seen before but it also stimulates some genuinely interesting mathematical thought. Above all, this book highlights the 'frailty of the intuition we routinely use to guide us through our everyday lives' and that, in my mind, is no bad thing.
Mathematical Intelligencer - Christina Birkenhake
I recommend the book to everyone interested in entertaining mathematics.
Mathematical Reviews - Stan Wagon
This book discusses such problems in a generally accessible way, but it does not shy away from using rigorous mathematical arguments to explain them. . . . Some of these topics are quite familiar, but even so I found the discussions clear and often learned some new and quite surprising tidbits.
Kybernetes - C.J.H. Mann
Those that spend their working lives avoiding mathematics by approaching their problems in all sorts of different ways will benefit from looking at this text, even if it involves following through but one single problem and its mathematical solution.
Mathematics Teacher - Anne Papakonstantinou
The book is perfect for independent or group study for students in advanced high school mathematics classes or university-level undergraduate mathematics classes. Selected chapters are suitable for discussion during professional development sessions aimed at engaging mathematics teachers in rigorous mathematics investigations and discussions.
Zentralblatt MATH - Yuri V. Rogovchenko
This lovely book will attract the attention of readers who are interested in recreational mathematics like mathematical puzzles and paradoxes.
Mathematics in School - John Sykes
Havil has an excellent mix of an interesting history of each topic and clear and lucid solutions to the problems. . . . Havil's strength is the historical background he gives to each topic and his style of writing which is so easy to read. . . . An interesting and challenging book well worth reading.
From the Publisher
"Nonplussed! is a collection of lovely paradoxes: facts that are provable logically but are nevertheless seriously counterintuitive...It is an exciting book. It should be in every...college library. It would even be the right gift for mathematicians and anyone who uses mathematics—economists, business analysts and many others—and indeed for anyone who would claim to be educated."—Peter M. Neumann, Times Higher Education Supplement

"This is a splendid collection of articles, inspired by Martin Gardner's writings. Old conundrums are given new twists and applications, newer perplexing ideas are described with panache. The forthcoming companion book has a high standard to maintain."—John Haigh, London Mathematical Society Newsletter

"It is therefore recommended that Julian Havil's headmaster award him further sabbatical leave for the purpose of producing a sequel to this welcome addition to the mathematical literature."—Peter Ruane, MAA Review

"A review of a book as good as this must either repeat the positive adjectives other reviewers have used, or require a very large thesaurus. Since I find myself in complete agreement with all of the following words from other reviews, I will repeat them immediately: marvelous, crystal-clear, great, amazing, stimulating, delightful, fascinating, strong, surprising, classic, interesting, eclectic, insightful, magnificent. That one book could encourage such gushing praise seems as unlikely as one book being able to cram in a great variety and depth of mathematical problems, colourful historical anecdotes, significant nods to ethno-mathematics, difficult but well-explained proofs, clear and engaging prose and beautiful diagrams. Yet Havil's book succeeds on all accounts...The brilliant writing, the wonderful problems, the weaving together of past and future, games and discovery, and world number cultures will have you returning to this ageless book time and again."—Phil Wilson, Plus Magazine

"This fascinating expedition by Havil through some engaging and often surprising mathematical and statistical oddities is more demanding than the usual 'popular math book' it is billed...All topics are covered by an always carefully crafted mathematical exposition, not leaving out necessary preliminaries and providing rigorous proofs."—J. Mayer, Choice

"Even many high school students without a calculus background will benefit from the problems contained in the book. . . . The book contains a little algebra, some geometry, and a great deal of probability. It could serve as recreational reading for teachers as well as for student use in a probability course or courses following algebra 2. Mathematics clubs and teams would also find Nonplussed! useful."—Paul Kelley, Mathematics Teacher

"This is a fun book containing many diverse problems that I had not seen before but it also stimulates some genuinely interesting mathematical thought. Above all, this book highlights the 'frailty of the intuition we routinely use to guide us through our everyday lives' and that, in my mind, is no bad thing."—Nathan Green, Mathematics Today

"I recommend the book to everyone interested in entertaining mathematics."—Christina Birkenhake, Mathematical Intelligencer

"This book discusses such problems in a generally accessible way, but it does not shy away from using rigorous mathematical arguments to explain them. . . . Some of these topics are quite familiar, but even so I found the discussions clear and often learned some new and quite surprising tidbits."—Stan Wagon, Mathematical Reviews

"Those that spend their working lives avoiding mathematics by approaching their problems in all sorts of different ways will benefit from looking at this text, even if it involves following through but one single problem and its mathematical solution."—C.J.H. Mann, Kybernetes

"The book is perfect for independent or group study for students in advanced high school mathematics classes or university-level undergraduate mathematics classes. Selected chapters are suitable for discussion during professional development sessions aimed at engaging mathematics teachers in rigorous mathematics investigations and discussions."—Anne Papakonstantinou, Mathematics Teacher

"This lovely book will attract the attention of readers who are interested in recreational mathematics like mathematical puzzles and paradoxes."—Yuri V. Rogovchenko, Zentralblatt MATH

"Havil has an excellent mix of an interesting history of each topic and clear and lucid solutions to the problems. . . . Havil's strength is the historical background he gives to each topic and his style of writing which is so easy to read. . . . An interesting and challenging book well worth reading."—John Sykes, Mathematics in School

Zentralblatt MATH Database
This lovely book will attract the attention of readers who are interested in recreational mathematics like mathematical puzzles and paradoxes.
— Yuri V. Rogovchenko
Read More Show Less

Product Details

  • ISBN-13: 9781400837380
  • Publisher: Princeton University Press
  • Publication date: 8/2/2010
  • Sold by: Barnes & Noble
  • Format: eBook
  • Edition description: Course Book
  • Pages: 216
  • Sales rank: 1,306,660
  • File size: 6 MB

Meet the Author

Julian Havil is a former Master at Winchester College, England, where he taught mathematics for more than thirty years. He is the author of "Gamma: Exploring Euler's Constant" and "Impossible?: Surprising Solutions to Counterintuitive Conundrums" (both Princeton).
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Table of Contents

Preface xi
Acknowledgements xiii
Introduction 1
Chapter 1: Three Tennis Paradoxes 4
Chapter 2: The Uphill Roller 16
Chapter 3: The Birthday Paradox 25
Chapter 4: The Spin of a Table 37
Chapter 5: Derangements 46
Chapter 6: Conway's Chequerboard Army 62
Chapter 7: The Toss of a Needle 68
Chapter 8: Torricelli's Trumpet 82
Chapter 9: Nontransitive Effects 92
Chapter 10: A Pursuit Problem 105
Chapter 11: Parrondo's Games 115
Chapter 12: Hyperdimensions 127
Chapter 13: Friday the 13th 151
Chapter 14: Fractran 162
The Motifs 180
Appendix A: The Inclusion-Exclusion Principle 187
Appendix B: The Binomial Inversion Formula 189
Appendix C: Surface Area and Arc Length 193
Index 195
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First Chapter

Nonplussed!

MATHEMATICAL PROOF OF IMPLAUSIBLE IDEAS
By Julian Havil

PRINCETON UNIVERSITY PRESS

Copyright © 2007 Julian Havil
All right reserved.

ISBN: 978-0-691-14822-9


Chapter One

THREE TENNIS PARADOXES

So that as tennis is a game of no use in itself, but of great use in respect it maketh a quick eye and a body ready to put itself into all postures; so in the mathematics, that use which is collateral and intervenient is no less worthy than that which is principal and intended. Roger Bacon

In this first chapter we will look at three examples of sport-related counterintuitive phenomena: the first two couched in terms of tennis, the third intrinsically connected with it.

Winning a Tournament

The late Leo Moser posed this first problem during his long association with the University of Alberta. Suppose that there are three members of a club who decide to embark on a private tournament: a new member M, his friend F (who is a better player) and the club's top player T.

M is encouraged by F and by the offer of a prize if M wins at least two games in a row, played alternately against himself and T.

It would seem sensible for M to choose to play more against his friend F than the top player T, but if we look at the probabilities associated with the two alternative sequences of play, FTF and TFT, matters take on a very different look. Suppose that we write f as the probability of M beating F and t as the probability of M beating T (and assume independence).

If M does choose to play F twice, we have table 1.1, which lists the chances of winning the prize.

This gives a total probability of winning the prize of

[P.sub.F] = ftf + ft(1 - f) + (1 - f)tf = ft(2 - f).

Now suppose that M chooses the seemingly worse alternative of playing T twice, then table 1.2 gives the corresponding probabilities, and the total probability of winning the prize becomes

[P.sub.T] = tf t + tf (1 - t) + (1 - t)ft = ft(2 - t).

Since the top player is a better player than the friend, t < f and so 2 - t > 2 - f, which makes ft(2 - t) < ft(2 - f) and PT < PF. Therefore, playing the top player twice is, in fact, the better option.

Logical calm is restored if we look at the expected number of wins. With FTF it is

[E.sub.F] = 0 x (1 - f)(1 - t)(1 - f) + 1 x {f(1-t)(1-f) + (1-f)t(1-f) + (1-f)(1-t)f} + 2 x {ft(1 - f) + f(1 - t)f + (1 - f)tf} + 3 x ftf = 2f + t

and a similar calculation for TFT yields ET = 2t + f .

Since f < t, 2f - f < 2t - t and so 2f + t < 2t + f, which means that EF < ET - and that we would expect!

Forming a Team

Now let us address a hidden pitfall in team selection.

A selection of 10 tennis players is made, ranked 1 (the worst player, W) to 10 (the best player, B). Suppose now that W challenges B to a competition of all-plays-all in which he can chose the two best remaining players and B, to make it fair, must choose the two worst remaining players.

The challenge accepted, W's team is TW = {1, 8, 9} and B's team is [T.sub.B] = {10, 2, 3}. Table 1.3 shows the (presumed) inevitable outcome of the tournament; at this stage we are interested only in the upper left corner. We can see that W's disadvantage has not been overcome since [T.sub.B] beats [T.sub.W] 5 games to 4.

The remaining players are {4, 5, 6, 7} and W reissues the challenge, telling B that he can add to his team one of the remaining players and then he would do the same from the remainder; of course, both B and W choose the best remaining players, who are ranked 7 and 6 respectively. The teams are now [T.sub.W] = {1, 8, 9, 6} and [T.sub.B] = {10, 2, 3, 7} and the extended table 1.3 now shows that, in spite of B adding the better player to his team, the result is worse for him, with an 8-8 tie.

Finally, the challenge is reissued under the same conditions and the teams finally become [T.sub.W] = {1, 8, 9, 6, 4} and [T.sub.B] = {10, 2, 3, 7, 5} and this time the full table 1.3 shows that [T.sub.W] now beats [T.sub.B] 13-12.

A losing team has become a winning team by adding in worse players than the opposition.

Table 1.4 shows, in each of the three cases, the average ranking of the two teams. We can see that in each case the [T.sub.B] team has an average ranking less than that of the [T.sub.W] team and that the average ranking is increasing for [T.sub.B] and decreasing (or staying steady) for [T.sub.W] as new members join. This has resonances with the simple (but significant) paradox known as the Will Rogers Phenomenon.

Interstate migration brought about by the American Great Depression of the 1930s caused Will Rogers, the wisecracking, lariat-throwing people's philosopher, to remark that

When the Okies left Oklahoma and moved to California, they raised the intellectual level in both states.

Rogers, an 'Okie' (native of Oklahoma), was making a quip, of course, but if we take the theoretical case that the migration was from the ranks of the least intelligent of Oklahoma, all of whom were more intelligent than the native Californians(!), then what he quipped would obviously be true. The result is more subtle, though. For example, if we consider the two sets A = {1, 2, 3, 4} and B = {5, 6, 7, 8, 9}, supposedly ranked by intelligence level (1 low, 9 high), the average ranking of A is 2.5 and that of B is 7. However, if we move the 5 ranking from B to A we have that A = {1, 2, 3, 4, 5} and B = {6, 7, 8, 9} and the average ranking of A is now 3 and that of B is 7.5: both average intelligence levels have risen.

If we move from theoretical intelligence levels to real-world matters of the state of health of individuals, we approach the medical concept of stage migration and a realistic example of the Will Rogers phenomenon. In medical stage migration, improved detection of illness leads to the fast reclassification of people from those who are healthy to those who are unhealthy. When they are reclassified as not healthy, the average lifespan of those who remain classified as healthy increases, as does that of those who are classified as unhealthy some of whose health has been poor for longer. In short, the phenomenon could cause an imaginary improvement in survival rates between two different groups. Recent examples of this have been recorded (for example) in the detection of prostate cancer (I. M. Thompson, E. Canby-Hagino and M. Scott Lucia (2005), 'Stage migration and grade inflation in prostate cancer: Will Rogers meets Garrison Keillor', Journal of the National Cancer Institute 97:1236-37) and breast cancer (W. A. Woodward et al. (2003), 'Changes in the 2003 American Joint Committee on cancer staging for breast cancer dramatically affect stage-specific survival', Journal of Clinical Oncology 21:3244-48).

Winning on the Serve

Finally, we revert to lighter matters of tennis scoring and look at a situation in which an anomaly in the scoring system can, in theory, be exposed.

The scoring system in lawn tennis is arcane and based on the positions of the hands of a clock. For any particular game it is as follows.

If a player wins his first point, the score is called 15 for that player; on winning his second point, the score is called 30 for that player; on winning his third point, the score is called 40 for that player, and the fourth point won by a player causes the player to win, unless both players have won three points, in which case the score is called deuce; and the next point won by a player is scored 'advantage' for that player. If the same player wins the next point, he wins the game; if the other player wins the next point the score is again called deuce. This continues until a player wins the two points immediately following the score at deuce, when that player wins.

The great tennis players of the past and present might be surprised to learn that, with this scoring system, a high quality tennis player serving at 40-30 or 30-15 to an equal opponent has less chance of winning the game than at its start.

We will quantify the players being evenly matched by assigning a fixed probability p of either of them winning a point as the server (and q = 1 - p of losing it); for a high quality player, p will be close to 1. The notation P(a, b) will be used to mean the probability of the server winning the game when he has a points and the receiver b points; we need to calculate P(40, 30) and P(30, 15) and compare each of these with P(0, 0), which we will see will take some doing!

First, notice that the position at 'advantage' is the same as that at (40, 30), which means that the situation at deuce, when divided into winning or losing the next point, is given by

P(40, 40) = pP(40, 30) + qP(30, 40),

also, using the same logic, we have

P(30, 40) = pP(40, 40) and P(40, 30) = p + qP(40, 40).

If we put these equations together, we get

P(40, 40) = p(p + qP(40, 40)) + q(pP(40, 40))

and so

P(40, 40) = [p.sup.2]/1 - 2pq.

Using the identity 1 - 2pq = [(p + q).sup.2] - 2pq = [p.sup.2] + [q.sup.2] we have the more symmetric form for the situation at deuce,

P(40, 40) = [p.sup.2]/[p.sup.2] + [q.sup.2].

and this makes

P(30, 40) = pP(40, 40) = [p.sup.3]/[p.sup.2] + [q.sup.2]

and the first of the expressions in which we have interest is then

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

Now we will find the expression for P(30, 15), which takes a bit more work, made easier by the use of a tree diagram which divides up the possible routes to success and ends with known probabilities, as shown in figure 1.1.

Every descending route is counted to give

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

and so we have found the second of our expressions

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

We only need the starting probability P(0, 0), which is by far the hardest goal, and to reach it without getting lost we will make use of the more complex tree diagram in figure 1.2, which again shows the ways in which the situations divide until a known probability is reached. We then have

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

and the final expression needed is

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

Plots of the three probabilities, shown in figures 1.3-1.5, for all values of p (remembering that q = 1 - p) show that they have very similar behaviour to one another, but there are intersections and if we plot the pairs {P(0, 0), P(30, 15)} and {P(0, 0), P(40, 30)} on the same axes for large p we can see them. This is accomplished in figures 1.6 and 1.7.

Of course, to find those intersections we need to do some algebra.

The Intersection of P(30, 15) and P(0, 0)

To find the point of intersection we need to solve the formidable equation

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

again remembering that q = 1 - p.

Patience (or good mathematical software) leads to the equation in p,

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

which has repeated trivial roots of p = 0, 1 as well as the roots of the quadratic equation 8[p.sup.2] - 4p - 3 = 0.

The only positive root is [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] ... and for any p < 0.911 437 ... we will have P(0, 0) < P(30, 15) and the result for this case is established.

The Intersection of P(40, 30) and P(0, 0)

This time the equation to be solved is

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

and, after a similarly extravagant dose of algebra, this reduces to

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

which again has trivial roots of p = 0, 1.

The remaining cubic equation 8[p.sup.3] - 4[p.sup.2] - 2p - 1 = 0 has the single real root,

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

which evaluates to p = 0.919 643 ....

Again, for any p < 0.919 6 ..., we will have P(0, 0) < P(40, 30), with the paradox once again established.

In conclusion, two equal players who are good enough to win the point on their serve just over 90% of the time are better off at the game's start than they are when the score is either 30-15 or 40-30 in their favour.

Chapter Two

THE UPHILL ROLLER

Mechanics is the paradise of the mathematical sciences because by means of it one comes to the fruits of mathematics. Leonardo da Vinci

An Advertisement for a Book

The Proceedings of the Old Bailey dated 18 April 1694 chronicles a busy day devoted to handing down justice, in which 29 death sentences were passed as well as numerous orders for brandings; there would have been 30 death sentences had not one lady successfully 'pleaded her belly' (that is, proved that she was pregnant). The business part of the document ends with a list of the 29 unfortunates and continues to another list; this time of advertisements (rather strange to the modern mind), which begins with the following paragraph:

THE Ladies Dictionary: Being a pleasant Entertainment for the Fair Sex; Work never attempted before in English. The Design of this Work is universal, and concerns no less than the whole Sex of Men in some regard, but of Women so perfectly and neatly, that 'twill be serviceable to them in all their Concerns of Business, Life, Houses, Conversations.

Tempting though it is to delve into the details of what suggests itself as a bestselling book, we move to the second advertisement.

Pleasure with Profit: Consisting of Recreations of divers kinds, viz. Numerical, Geometrical, Mathematical, Astronomical, Arithmetical, Cryptographical, Magnetical, Authentical, Chymical, and Historical. Published to Recreate Ingenious Spirit, and to induce them to make further scrutiny how these (and the like) Sublime Sciences. And to divert them from following such Vices, to which Youth (in this Age) are so much inclin'd. By William Leybourn, Philomathes.

Presumably, those who were tried at the assizes had been given insufficient access to the work and we will touch on only a small part of it ourselves, to be precise, pages 12 and 13.

William Leybourn (1626-1719) (alias Oliver Wallingby) was in his time a distinguished land and quantity surveyor (although he began his working life as a printer). Such was his prestige, he was frequently employed to survey the estates of gentlemen, and he helped to survey the remnants of London after the great fire of 1666. Also, he was a prolific and eclectic author. In 1649 he published (in collaboration with one Vincent Wing) Urania Practica, the first book in English devoted to astronomy. After this came The Compleat Surveyor, which first appeared in 1653 and ran to five editions, and is regarded as a classic of its kind. His 1667 work, The Art of Numbering by Speaking Rods: Vulgarly Termed Napier's Bones, was significant in bringing them further into the public eye.

In 1694 he had published the recreational volume Pleasure with Profit, the opening page of which is shown in figure 2.1.

We can readily agree with the following sentiment expressed in the book:

But leaving those of the Body, I shall proceed to such Recreations as adorn the Mind; of which those of the Mathematicks are inferior to none.

And having done so we can then concentrate on a delightful mechanical puzzle described in the book and attributed to one 'J.P.', which has become known as the Uphill Roller.

Figures 2.2 and 2.3 show pages 12 and 13 of the book, which detail the construction of a double cone and two inclined rails along which the cone can roll - uphill. His final paragraph explains the paradox, pointing out that the important issue is that, even though the cone does ascend the slope, its centre of mass will descend if the measurements are just right, which ensures that, although one's senses might be confounded, the law of gravity is not.

An Explanation

Before we examine Leybourn's explanation, we will look at the matter through modern eyes, using elementary trigonometry to study it. Figures 2.4, 2.5 and 2.6 establish the notation that we need and parametrize the configuration in terms of three angles: a, the angle of inclination of the sloping rails; s, the semi-angle between the rails, measured horizontally at floor level; [??], the semi-angle at an apex of the double cone. Write a and b as the heights of the lower and upper ends of the rails and r as the radius of the double cone. An x/y coordinate system is then set up as shown in figure 2.4.

(Continues...)



Excerpted from Nonplussed! by Julian Havil Copyright © 2007 by Julian Havil. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

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