AHA! Puzzle This
By Michael H. Pryor
MAKE’s favorite puzzles. (When you’re ready to check your answers, visit makezine.com/11/aha.)
start at the back of the line and ask each gnome to
guess the color of his own hat. Each gnome can only
answer either “red” or “blue.” If he gives the wrong
answer, he will be led off to work on the wizard’s
landscaping for the rest of eternity. If he answers correctly, he will be returned to his own garden. Then the
wizard will move on to the next gnome in line.
All of the gnomes will be able to hear the answers
of the gnomes behind them, but they will not know if
they were led off to forced labor or if they answered
correctly and were set free. The gnomes are allowed
to consult and agree on a strategy beforehand (while
the wizard listens in) but after being lined up, they will
not be able to communicate in any other way besides
their answer of “red” or “blue” (in other words, they
Point of Gnome Return won’t be able to change the pitch of their voice or
One hundred very smart garden gnomes are give any other clues to the other gnomes once they
snatched from their homes by an evil wizard. He are in line and the hats are placed on their heads).
tells them he is going to line them all up in a row, and What strategy should the gnomes use to maximize
place a red or blue hat on each of their heads. They the total number of gnomes that will be set free?
won’t be able to see the color of their own hats or Hint: They can do pretty well, even if the wizard hears
anyone’s behind them, but they will be able to see the their plan and puts the hats on in such a way to
hats of the gnomes in front of them. The wizard will thwart whatever idea they come up with.
Human Race
Illustrations by Roy Doty
Five makers (Ben, Mark, Jason, Ruth,
and Joel) raced in an extravaganza for
alternative transportation. They competed in five separate races: a Segway
race, a bicycle race, a hybrid car race, a
skateboard race, and a roller skate race.
Points were given as follows: 5 points
for first place, 4 points for second, 3
points for third, 2 points for fourth, and
1 point for last place. Overall scores
were determined by adding up the
individual scores from each race.
Ben got the highest number of points:
24. Jason finished in the same place in
four out of the five races. Joel came in
first in the skateboard race, and third in the roller
skate race.
The final total rankings for the races were: Ben,
Mark, Jason, Ruth, and then Joel. There were no ties
in any individual races, and no two racers had the
same total score.
What place did Mark come in during the skateboard race?
Michael Pryor is the co-founder and president of Fog Creek Software. He runs a technical interview site at techinterview.org.
Make: 181
