Thanks to Suzanne Alejandre for this activity and its accompanying lesson plan, and Mike Morton for the nifty Applet.

Magic Squares

Activity of the Month

October 1996

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Each month the Math Forum sponsors a student activity that can be done locally and shared globally. There are:

  Magic Square Puzzle Activity  

For this month's activity,
we'll discover how to make a 3x3 magic square.
 

What is a magic square?

In a magic square, the rows, columns, and diagonals all add up to the same number.

Let's begin with the first three numbers:

Can you fill in the empty cells?

Need help?

Definition:

Some mathematicians define a magic square formally as an arrangement of the numbers from 1 to n^2 (n-squared) in an nxn matrix, with each number occurring exactly once, and such that the sum of the entries of any row, any column, or any main diagonal is the same.

Discussion suggestions:

  1. What is the sum of each row, column, diagonal of the magic square? Can a square be made that results in a different sum? [Advanced question: Why or why not?]
  2. How did you figure out what numbers to use and where to put them in the square?
  3. What number did you place in the middle? Is this the only number that can go in the middle? [Advanced question: Why or why not?]
  4. If we start with a puzzle like the one above, is there only one solution? [Advanced question: Why or why not?]
  5. [Advanced question: Can you show that the sum of the entries of any row, any column, or any main diagonal must be n(n^2+1)/2?]

Interactive exploration: a Magic Square Java Applet

A lesson plan for the classroom, by Suzanne Alejandre.

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