每周数学 （二十四）3x3 magic square

 *3x3 magic square puzzles* is solved by finding the values that make the sums all rows, columns and diagonals equal to the same value. ... 

The normal variations of these puzzles (in other words, 3x3 puzzles that contain only 1-9 in their cells) have a magic constant of 15 no matter how the numbers are arranged.

1.

Sum =1+2+3+....+9 =(1+9)x9/2

=45

45/3=15

2. 15=

9+1+5

9+2+4

8+1+6

8+2+5

8+3+4

7+2+6

7+3+5

6+4+5

Total eight equations

5 appears 4 times: placed at centre

8,6,4,2 appear 3 times: placed at corners

9,7,3,1 appear 2 times: placed at the sides

8.  1.   6.

3.  5.   7. 

4.  9.   2. 

*One and only one solution.*