Archive for the ‘Sudoku’ Category

Happy Pi Day 2015!

March 10, 2015

Pi Day is coming up, and this year is a special one:  instead of just 3.14 on March 14 we get 3.1415.  Woo hoo!  So grab a Sudoku

(from Brainfreeze Puzzles:  Digits 1-9 in each row, column, and square, plus digits 31415926 in each block of pink)

and grab a beverage of your choice


and enjoy.  Happy Pi Day!

If it’s Pi Day, that means…

March 14, 2011

Brainfreeze Puzzles must have a new Pi Day Puzzle up — woo hoo!!!!!

The Rules are to fill in this pie-shaped circle so that the numbers 1 through 12 appear:

  • exactly once in each double-wedge of the same color,
  • exactly once in each pair of opposite wedges, and
  • exactly once in each ring around the center.

As in previous years, they are having a contest for correct entries (information on this website and this pdf file), so no hints or solutions are to be posted in the comments until the contest closes on June 1.  [If/when they print a solution, we’ll post a link to it.]

If you missed Brainfreeze’s earlier puzzles, here are the ones from:




Pi Day Sudoku Is Back!

March 9, 2010

You laughed in 2008.

You cried in 2009.

This March, from the producers of Naked Sudoku*, comes…

Pi Day Sudoku 2010


As in past years, there is also a contest** associated with the puzzle, but who needs a contest when you’ve got a puzzle with the (conjectured) minimum number of clues (18 – in this puzzle, the first 18 digits of π) for a unique solution of a rotationally symmetric puzzle?  Here’s a printable PDF so you can take the puzzle with you to your next meeting lunch break.

Happy solving!

*Brainfreeze Puzzles, in case you were wondering.
**Also as in past years, we will not allow a solution to be posted until after the June 1 deadline.  Thank you for your cooperation.

Carnival of Maths #59 is up!

November 7, 2009

clown at the carnivalThe Number Warrior is hosting this month’s carnival!  It’s up here, and I was impressed with the entries [both in number and quality].  Plus, there was even something on Bourbaki, though not the symbol I wrote on earlier.

I also really like the post right before the Carnival, about a possible case of cheating at the 2009 Philadelphia Inquirer Sudoku National Championship.  You can find some of the contest Sudoku puzzles at this pdf.

Now I want to try some Sudoku:  here’s one that’s a jigsaw puzzle (created by A.R. Nonenmacher and published under GNU-FDL)


Pi Day Sudoku 2009

March 9, 2009

Remember Pi Day Sudoku 2008?  Well the folk at Brainfreeze Puzzles have done it again!  Here’s their 2009 challenge:


Each row, column, and region contains the digits 1-9 exactly once plus three π symbols.  There’s a printable .pdf file here.

As a bonus, if you send a correct solution in to Brainfreeze puzzles in the next couple months, you’re eligible for a drawing for their book on Color Sudoku!  More details are on their website.

Happy Pi Day Week!

Edited 10/31 to add that the solution hasn’t been posted on the Brainfreeze site yet, but since it’s well past the contest deadline we approved a comment that has the solution (below).


November 19, 2008

kenkenproblemBarbie might think math is hard, but perhaps she’d be willing to try this game.  I just heard about it yesterday around the water cooler copier (Thanks Lynn!).  It’s a little bit like Killer Sudoku, but with operations other than just addition.

The initial grid is a square, perhaps 4×4 or 6×6.  Like Sudoku, the digits 1-4 or 1-6 are put in cells so that each row contains exactly one of the digits and each column contains exactly one of the digits.

In addition, there are groups of cells (like the cages in Killer Sudoku).  In the corner is a number and an operation.  If the digits in a group are put together with that operation, they form the given number.  For example, if there are two cells with “8x” in the corner, the digits multiply to 8, and so must be 1&8 or 2&4 in some order.  Likewise, “2/” (using / for division) could be 1&2, 2&4, 3&6, or 4&8 where the pairs are in either order.  While you can’t repeat digits in any row or column, you can repeat digits in a group of cells.

Here’s one to try, courtesy of SGBailey.


(You can find the answers in the place that always gives you answers.)

If you search for KenKen there seem to be several sites where you can get your daily fix (including the New York Times), but most require registration.  And apparently in some of the harder versions the operation is left off so that you know the answer, but not whether it is a sum, product, quotient, or different.  I can totally imagine a variation that uses multiple operations in a single group of cells, but as far as I know that hasn’t been invented yet.

Worms and Sudoku

September 13, 2008

In case you thought worms only did calculus, the folk over at Brainfreeze Puzzles have created a puzzle to guarantee your work stays undone and your house remains messy you have a lot of fun. Or frustration. Or both. And you might even win a copy of their book Color Sudoku!

Note: We’ll post a link to the solution when it becomes officially available on the main site [which will be, presumably, sometime after the contest ends].

MathFest Sudoku!

June 17, 2008

The folk at Brainfreeze Puzzles (creator of the famous Pi Day Sudoku) have created a new puzzle for MathFest 2008 in Madison this August!

The official rules are:

Each row, column, and block must contain each digit 1-9 exactly once. Since the middle block is missing, rows and columns that intersect the middle block will have only six visible numbers. In addition, each “Worm” in the puzzle contains numbers that increase from tail to eyes (although not necessarily consecutively). For example, a worm of length four could contain 2, 5, 7, 9 in that order, from tail to eyes.

Sudoku posted with permission. Thanks!

Pi Day Sudoku Solution

May 6, 2008

Remember Pi Day Sudoku from Brainfreeze Puzzles?

If you were wanting the answer, it’s been posted!  You can find the solution here.

Pi Day Sudoku

March 12, 2008

In honor of Pi Day, Brainfreeze Puzzles (“we turn coffee into puzzles”) created a Pi Day Sudoku on a 12×12 grid.


The rules are a little different from standard Sudoku, in part because the blocks are jigsaw pieces rather than 3×3, and in part because the first 12 digits of π are used instead of the standard 1-9. Each row, each column, and each colored block (“jigsaw region”) contains the first 12 digits of pi

3 1 4 1 5 9 2 6 5 3 5 8

in some order. In particular, there are two 1s, one 2, two 3s, one 4, three 5s, one 6, no 7s one 8, and one 9.

As a bonus, on Brainfreeze’s Pi Day site there are instructions for how to (possibly) win an autographed book by completing the puzzle. Woo hoo!
The contest is over: you can find the solution here.

A Sudoku-Solving (Quantum) Computer

January 22, 2008

sudoku-by-l2g-20050714.jpgSo you bought a Sudoku Lotto ticket and now you’re having trouble solving it? Turn to a quantum computer! When D-Wave Systems, Inc. announced that it had created a 16-qubit quantum computer last year, they demonstrated its power in three ways: “searching for molecular structures that match a target molecule, creating a complicated seating plan, and filling in Sudoku puzzles.” (See First “Commercial” Quantum Computer Solves Sudoku Puzzles). According to D-Wave’s website, two months ago they unveiled a 28-qubit model; however, there’s no mention of its game playing skills.

For more about Quantum Computers, see How Stuff Works.

Juxtapositions: Sudoku Lotto

January 21, 2008

There I was, a mathematician in the grocery checkout line. Inexplicably, I found my eye drawn to the scratch-off lottery ticket machine. Unlike the proverbial punk in a Dirty Harry movie, I did feel lucky, and I surreptitiously slipped a couple bucks out of my wallet, hoping the cashier wouldn’t notice and take me for a fool.

One of the current scratch-off games offered by the New York Lottery is a SuDoKu game.


Juxtapositions: Killer Sudoku

December 23, 2007

killer-sudoku.jpgIn a comment on an earlier post aboout Sudoku and Kakuro, Batman mentioned a combination of the two games known alternately as Killer Sudoku, Samunamupure or Sum Number Place. As in traditional Sudoku, Killer Sudoku is played on a 9×9 grid in which the digits 1-9 are placed so that each digit appears once in each row, each column, and each 3×3 grid (nonet). As in Kakuro, groups of cells (cages) add to given sums, and within each cage the digits must be distinct. Click to read more and see an enlargement of the game pictured here at the left.

Sudoku and Kakuro

November 12, 2007

In recent years many people have played Sudoku, a number game in which a nine-by-nine grid is filled with the digits 1-9 so that each row, each column, and each group of nine squares contains exactly one of each digit. Read more about Sudoku and Kakuro