December 2007
Problem of the Month

Magic Square by Sidney Kravitz in Games Magazine October 2007



The three numbers in every row, column, and diagonal have the same sum.   This is called a magic square.   Three numbers are given.   Can you find the other six?
  25           30  
                 
        21        



Solution to the Problem:

  25     47     30  
  39     34     29  
  38     21     43  

To solve this, I assigned the letters A, B, C, D, E, and F to the six missing numbers:

  25     A     30  
  B     C     D  
  E     21     F  

Then, since I knew that each row, column, and diagonal add up to the same number, I wrote the following:
A + 25 + 30 = B + C + D = E + F + 21 =
25 + B + C = A + C + 21 = 30 + D + F =
25 + C + F = E + C + 30
Since these eight expressions are all equal, I can set any two of them equal to each other.
So, A + 25 + 30 = A + C + 21
     So, C = 34.
Then set E + F + 21 = E + C + 30 and replace C by 34 to obtain F = 43.
Now, we know the Magic Sum is 25 + C + F = 102.
So, E = 102 - 21 - 43 = 38.
Then B = 102 - 25 - 38 = 39.
Then D = 102 - 39 - 34 = 29.
Finally, A = 102 - 25 - 30.





Correctly solved by:

1. K. Sengupta Calcutta, INDIA
2. John Funk Ventura, California
3. Richard K. Johnson La Jolla, California
4. Les Walker Ventura, California


Send any comments or questions to: David Pleacher