
Frank Morgan's Math Chat

February 18, 1999
A ONEPAGE PROOF OF FERMAT?
MATH JOKES. Math Chat has received a number of mathematical jokes, most of them terrible. This week's winner is a riddle from Peter Hegarty:
RIDDLE. Which mathematical term is named after a wellknown American
politician?
The answer is near the end of this column.
OLD CHALLENGE (Joe Shipman). Select the best occurrence in the world of
each number from 1 to 10. For example, 12 is the number of eggs in a dozen
or the number of months in a year.
ANSWER. Here is the winning response compiled from John Robertson, Henry Ricardo, Bob Swanson, JeanPierre Carmichael, and Ryan Grove:
 Number of Earth's moons
 Romeo and Juliet
 Dimensions; Mazur, Ribet, and Wiles (contributors to the proof
of Fermat's Last Theorem)
 The Four Freedoms (FDR, 1941: freedom of speech, freedom of
worship, freedom from want, freedom from fear)
 Platonic solids [cube, octahedron, tetrahedron, dodecahedron,
icosahedron]
 Legs on insects
 Notes of the musical scale
 Cylinders in a V8 engine (such as in the Ferrari 308 series);
vegetables in V8 juice (tomatoes, carrots, celery, beets, parsley, lettuce,
watercress, and spinach)
 Planets; Beethoven symphonies
 Fingers
(Can readers improve on this list?) Then there is this from Al Zimmermann:
 The amount, in cents, of the recent postage increase for first
class US mail.
 The number of sides to every story.
 The number of moving parts in a Wankel engine.
 The number of Beatles.
 The number of players on a basketball team.
 The number of sodas in a sixpack.
 The number of days in a week.
 The number of days in a week, according to the Beatles.
 The number of months in a pregnancy.
 The number of years it seems the Clinton/Lewinsky scandal has
been going on.
Finally, in his beautiful response, David Shay relates that, "At the end of
the Seder night, which begins the Jewish holiday of Passover, it is common
to sing a song named 'Who Knows One.' This song gives an exact Jewish
answer to your challenge, in the range of 1 to 13. Here it is:
Thirteen are the attributes of God;
Twelve are the tribes of Israel;
Eleven were the stars in Joseph's dream;
Ten commandments were given on Sinai;
Nine is the number of the holidays;
Eight are the days to the service of the covenant;
Seven days there are in a week;
Six sections the Mishnah has;
Five books there are in the Torah;
Four is the number of the matriarchs;
Three is the number of the patriarchs;
Two are the tables of the covenant;
One is our God in heaven and earth."
NEW CHALLENGE. Critique the following short proof of Fermat's Last Theorem
sent in by reader Rob Connelly. (In perhaps the biggest mathematics news of
the century, Andrew Wiles recently came up with a very long and complicated
proof to this 350year old problem.)
Fermat's Last Theorem. The equation
(1) x^{n} + y^{n} = z^{n}
has no positive integer solutions for n > 2.
Proposed proof. Suppose there were such a solution. Since x
y, we may suppose x = y + a, z = y + b, with b > a positive integers.
Consider the integer N defined by
(2) z^{n 1} = x^{n 1} + y^{n 1} + N.
Then
x^{n} + y^{n} = z^{n} = z(x^{n 1} + y^{n 1 }+ N).
Solving for N yields:
N = [(y+a) ^{n 1} (ab) + y^{n 1} (b)]/(y+b) = [F(y)]/(y+b) ,
so y+b divides F(y) and
0 = F(b) = (ab) ^{n } + (b) ^{n}
0 = (ba) ^{n } + b^{n} > 0,
the desired contradiction.
ANSWER TO RIDDLE. The mathematical term named after a wellknown American
politician is "Algorithm."
(Readers are invited to continue to submit more jokes for future columns.)
Send answers, comments, and new questions by email to:
Frank.Morgan@williams.edu, to be eligible for Flatland and other book
awards. Winning answers will appear in the next Math Chat. Math Chat
appears on the first and third Thursdays of each month. Prof. Morgan's
homepage is at www.williams.edu/Mathematics/fmorgan.
Copyright 1999, Frank Morgan.