With a tip of the cap to Anza Power, here's a Fibonacci puzzle with smaller numbers.
In today's class, Mr. Bigollo taught his students the Fibonacci series and Golden Ratio.
He noted the series traditionally begins 0, 1, 1, 2, 3, 5, 8, ... , but actually any two
numbers, not necessarily in ascending order, can seed the process.
To make the subject compelling, Mr. Bigollo announces to the class that you have
proven yourself among the Brain Denizens as particularly adept at solving seemingly
impossible mathematical puzzles. Furthermore, you have accepted his invitation to
their session today to participate in a demonstration of the amazing properties of
the Fibonacci series. You stand and smile, graciously, at the adoring stares of the class.
To begin, Mr. B selects ten students to line up in the front of the classroom.
Amazingly, their names are Al, Bob, Chuck, Dave, Ed, Frank, Geoff, Hal, Irv and Jack.
Here's what he asks them to do. Al is to select an integer at random and whisper it to Chuck. Bob also selects an integer at random and whispers it to Chuck. Chuck sums the numbers he hears and whispers his sum and Bob's number to Dave. Dave sums the numbers he hears and whispers his and Chuck's sums to Ed. Ed sums the numbers he hears and whispers his and Dave's sums to Frank. Frank sums the numbers he hears and whispers his and Ed's sums to Geoff. Geoff sums the numbers he hears and whispers his and Frank's sums to Hal. Hal sums the numbers he hears and whispers his and Geoff's sums to Irv. Irv sums the numbers he hears and whispers his and Hal's sums to Jack. Jack sums the numbers he hears.
Finally, each student whispers his own sum [Al and Bob whisper their chosen integers]
to Mr. Bigollo, who writes the sum of the ten numbers on a sheet of paper, which he
then places in an envelope.
To clarify: the envelope contains the sum of the first ten Fibonacci numbers generated
by Al and Bob's initial integer choices. No one but Mr. Bigollo knows this sum.
The students take their seats and Mr. Bigollo invites you to the front of the classroom
and announces to the class that you are now prepared to announce the number
contained in the envelope.
Noting your shock, and before you can protest, Mr, B. smiles and says: Well that
would be impossible of course. So, you may have one piece of information. You may
ask one of the students what his sum was. [That eliminates Al and Bob, they didn't
sum anything, but neither of them alone could supply useful information.]
Now your reputation is on the line.
Which student do you ask, and what is the sum?