Sudoku Logic

In a stack of papers called Instruction.

  • Aug
  • 26
  • 2007

I know, I arrived late on this scene. Only last summer, I caught the Sudoku virus. It’s totally under control now, but for a while I couldn’t go to bed unless I’d worked through whatever Sudoku I was on. Actually, I still can’t leave a puzzle half finished, but I don’t spend time solving five or more of them each day.

Explain Your Thinking

Example of a Sudoku puzzleThrough all that number tic-tac-toe, numbers only fit in a box because there’s a voice in my head telling me so. “That can only be a five because there are fives in the other two big boxes and there needs to be a five in this column.” It’s not the rules of the game that stick with me, it’s my reasoning of why this box can only be a five, nothing else.

That’s the kind of explanation I want to hear from my students about literature, quotations on the board at the beginning of class, political beliefs, school policies, any opinion they have. But they often don’t consider other possibilities and tend to voice their arguments as if the rest of the world already agrees with them, as if they don’t need to explain their opinion.

Can Sudoku teach logic? Will working on Sudoku have an impact on logic expressed in other arguments? What if class started with Sudoku one day a week? Be sure to pick an easy puzzle at the beginning. Even more important, be sure you know the solution before you begin so that you can redirect if needed. As a class, work through why each box has certain numbers in it. After talking about a few boxes, making sure you get rid of all the “obvious” ones, students write silently for a few minutes, then share out. Here are the directions:

Now that we’ve talked about a few numbers and filled in some of the boxes in this puzzle, you need to fill in three more boxes on your own. Describe which box you’re filling in (3rd row, 4th column or something similar), tell which number fits in the box, and discuss why. Just so you’re sure, briefly run through reasons that box can be no other number than the one you pick. You should end up writing about 2 sentences for each box you fill in, a short paragraph in total. Be prepared to share your reasoning with others.

Where To Go For Sudoku

Web Sudoku logoIf you have a projector set up in the classroom, use Web Sudoku. You can just click and type numbers with ease, hitting “Clear” between classes to reset the whole thing. Don’t use their print feature, hoping to get this puzzle onto an overhead. It looks like a good idea, but it doesn’t work well. Puzzles print across two pages. But shrinking things down to fit on a single page causes some of the grid lines disappear. Neither case is ideal.

Daily SuDoku logoIf you need to print out the puzzle, use Daily SuDoku. Their print feature works great. The site downloads a PDF that you can print onto an overhead. The PDF should be on your desktop within seconds. Click to open it and you have a puzzle that fits onto a single page and looks nice in the end.

Another possibility is to use Excel. I put together a template for you that creates one big Sudoku to use on a projector and automatically creates smaller versions of that puzzle to give your students, six to a page. Find a Sudoku generator (again,Web Sudoku and Daily SuDoku are good sources, but books work well, too) and type the numbers on your own. Since you have complete control using this method, you can either print out the spreadsheet on an overhead or project it in the classroom from your computer.

1 comment

1. Ryan says:

[2/11/2011 - 11:34 pm]

Another good game for teaching logic is Mastermind. A version that works well on a projector can be found at:

It works well when played as a group and they have to discuss their reasoning.