Hello! I’M tHe new eDItor
oF tHe Puzzles seCtIon.
while it’s probably the coolest
job at Contingencies, it comes
with a lot of pressure. Many of
you open each issue expecting
a new puzzle that’s neither too
easy nor too hard, a puzzle that
you haven’t seen before, and,
perhaps, a puzzle that calls upon
different mathematical abilities
from those puzzles published in
the past few issues.
For many years I would open
Contingencies, go straight to the puzzles page
and read it in reverse order. First, to
check to see if my name made it to the
solver list, then to read the solution to
the previous issue’s puzzle, and finally
to read the new puzzle (occasionally
wondering why the story was so long)
and begin pondering whether I would
be able to solve it.
Now I can add to this routine the
extra pressure of replacing Mark
Danburg-Wyld. He did a great job challenging readers of this section for the
past five years, and I aspire to reach his
competence in combining math and entertainment. Since I’m only starting my
tenure as editor, all feedback is welcome
(especially positive feedback).
I clearly remember being introduced
to the nine coins problem in the second
grade: “There are nine coins; one of them
is counterfeit and lighter than the real
Solutions may be emailed to
In order to make the solver list,
your solutions must by received
by Jan. 31, 2013.
ones. How does one find the fake coin
by using the balance scale two times?” I
couldn’t solve it on my own, but the solution was really fascinating, and I didn’t
stop thinking about for days (or perhaps
weeks). It became a burning reminder
that not all solutions are created equal;
there are very clever ways of doing things
in life, and one should stop and think before tackling a complex problem.
In the spirit of that lesson, here’s a
compilation of other, less familiar, weighing problems.
First, there are 10 piles of coins. One
pile contains only fake coins that weigh
nine grams. The other groups contain
only real coins that weigh 10 grams. Us-
ing an electronic scale, what is the least
number of weighings you need to under-
take to determine which pile contains
the fake coins? Note: Unlike the balance
scale, which allows you to compare the
relative weight of two piles, an electron-
ic scale determines the exact weight of
a single pile.