## MatheMUSEments

Articles for kids about math in everyday life, written by Ivars Peterson for Muse magazine.

## June 19, 2007

### Sudoku Mania

Millions of people around the world can't get started every day without their sudoku fix. Have you joined them?

A sudoku puzzle usually consists of a nine-by-nine grid. Some of the spaces contain numbers; the rest are blank. Your goal is to fill in the blanks with numbers from 1 to 9 so that each row, each column, and each of the nine three-by-three blocks making up the grid contains just one of each of the nine numbers. (Sudoku means "single number" in Japanese.)

Sudoku puzzles are basically logic puzzles. You don't need math to solve them. The numbers could just as easily be nine different shapes, colors, or letters of the alphabet. A smaller grid also works. For example, kids can try to solve simple puzzles that have four-by-four grids with two-by-two boxes.

An easy sudoku. Just fill in the blanks with the numbers 1 through 4.

Mathematicians have calculated that there are 6,670,903,752,021,072,936,960 nine-by-nine number patterns that can be turned into sudoku puzzles. If you were to do one every second of every day, it would take many, many times the age of the universe to complete them all. As it is, even expert solvers can take as long as 30 minutes to solve a challenging sudoku. So, there are plenty of puzzles to keep everyone busy for a long, long time.

If you're eager to join the hordes devouring these puzzles, here are a few hints on how to get started. If you're working on paper, pencil in numbers that might go in a blank until there is only one choice. Look especially for rows, columns, or blocks that have numbers in five or more spaces. That allows you to narrow down the possibilities more quickly.

Another easy sudoku. Just fill in the blanks with the numbers 1 through 6.

Whatever strategy you use, doing sudoku puzzles gives you a chance to sharpen your concentration and reasoning powers. But beware of the nasty frustration factor when you realize that, having just about completed a puzzle, you've got the same number in two spaces in the same row and you have to start all over again. Keep an eraser handy!

You can find some sample sudoku puzzles for kids at www.activityvillage.co.uk/sudoku_for_kids.htm.

Standard sudoku puzzles that you can do online are available at www.websudoku.com.

Additional information about sudoku puzzles, along with tips for solving them, can be found at www.sudoku.com.

Muse, October 2005, p. 25.