[math-fun] Miscounting errors
Anyone have a favorite puzzle in which miscounting plays a role? My favorite is the classic bookworm puzzle (see https://math.stackexchange.com/questions/1271651/how-is-this-true-bookworm-p... ). Another example: A man was born in 50 BC and died on the same day in 50 AD. How old was he when he died? I'm especially interested in puzzles that lend themselves to solvers committing fencepost errors, and off-by-one errors more generally. Jim Propp
A frog is at the bottom of a well just shy of ten feet deep. He can jump three feet up, but the walls of the well are slippery, so he slides back two feet each time. How many jumps does it take to get out of the well? On Sat, Nov 11, 2017 at 6:06 AM, James Propp <jamespropp@gmail.com> wrote:
Anyone have a favorite puzzle in which miscounting plays a role?
My favorite is the classic bookworm puzzle (see https://math.stackexchange.com/questions/1271651/how-is-this-true-bookworm-p... ).
Another example: A man was born in 50 BC and died on the same day in 50 AD. How old was he when he died?
I'm especially interested in puzzles that lend themselves to solvers committing fencepost errors, and off-by-one errors more generally.
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
-- Mike Stay - metaweta@gmail.com http://www.cs.auckland.ac.nz/~mike http://reperiendi.wordpress.com
Place a coin with radius 3 on the table, and then place a coin with radius 1 touching it and above it. Roll the small coin without slipping all the way around the large coin, until it is above it again. How many revolutions does the small coin make? Andy On Sat, Nov 11, 2017 at 8:06 AM, James Propp <jamespropp@gmail.com> wrote:
Anyone have a favorite puzzle in which miscounting plays a role?
My favorite is the classic bookworm puzzle (see https://math.stackexchange.com/questions/1271651/how-is-this-true-bookworm-p... ).
Another example: A man was born in 50 BC and died on the same day in 50 AD. How old was he when he died?
I'm especially interested in puzzles that lend themselves to solvers committing fencepost errors, and off-by-one errors more generally.
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
-- Andy.Latto@pobox.com
There's a classic one that's somewhat a counting issue: A doctor gives a patient 4 pills at noon, and the patient must take one every half hour - at what time does he run out/take the last pill?
I'm especially interested in puzzles that lend themselves to solvers committing fencepost errors, and off-by-one errors more generally.
Jim Propp
Or, how many times does the earth rotate around its axis in a year? On 11-Nov-17 11:08, Andy Latto wrote:
Place a coin with radius 3 on the table, and then place a coin with radius 1 touching it and above it. Roll the small coin without slipping all the way around the large coin, until it is above it again. How many revolutions does the small coin make?
Andy
On Sat, Nov 11, 2017 at 8:06 AM, James Propp <jamespropp@gmail.com> wrote:
Anyone have a favorite puzzle in which miscounting plays a role?
My favorite is the classic bookworm puzzle (see https://math.stackexchange.com/questions/1271651/how-is-this-true-bookworm-p... ).
Another example: A man was born in 50 BC and died on the same day in 50 AD. How old was he when he died?
I'm especially interested in puzzles that lend themselves to solvers committing fencepost errors, and off-by-one errors more generally.
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
On Nov 11, 2017, at 11:08 AM, Andy Latto <andy.latto@pobox.com> wrote:
Place a coin with radius 3 on the table, and then place a coin with radius 1 touching it and above it. Roll the small coin without slipping all the way around the large coin, until it is above it again. How many revolutions does the small coin make?
Andy I gave this on a mechanics exam, with equal radius coins. The instructions were to first work out the relationship between the two angular velocities (motion of the center, rotation about the center).
-Veit
participants (6)
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Andy Latto -
James Davis -
James Propp -
Mike Speciner -
Mike Stay -
Veit Elser