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Easy Puzzle #25 - One Possible Solution Approach…
NB:  There is only one final solution to this Sudoku puzzle…
Rules: Place a number from 1-9 in each empty cell so that each row, each column AND each 3x3 block contains all the numbers from 1-9.
A B C D E F G H I
1                  
2 AA BB CC Reference to 3x3 Blocks AA, BB & CC
3                  
4                  
5 DD EE FF Reference to 3x3 Blocks DD, EE & FF
6                  
7                  
8 GG HH II Reference to 3x3 Blocks GG, HH & II
9                  
A B C D E F G H I
1   1 9   3   6 4   Easy Puzzle #25 - October 25, 2005  © joe-ks.com
2 3 4           7 1 One possible Solution Method follows below…
3       1 9 4      
4     6 3     4    
5 9   4   5   1   7
6     7   8 9 2    
7       5 7 3      
8 2 7   8       9 6
9   8     6     1  
A B C D E F G H I
1   1 9   3   6 4   Step 1: #9 is in Rows 1 & 2: #9 MUST go in Cell G2
2 3 4         9 7 1
3       1 9 4      
4     6 3     4     Step 2: #4 is in Rows 4 & 5: #4 MUST go in Cell D6
5 9   4   5   1   7
6     7 4 8 9 2    
7       5 7 3       Step 3: #7 is in Rows 7 & 8: #7 MUST go in Cell G9
8 2 7   8       9 6      (cf #7 in Column I @ I5 excludes use of Cell I9)
9   8     6   7 1  
A B C D E F G H I
1   1 9   3   6 4   Step 4: #9 is in Columns A & C: #9 MUST go in Cell B7
2 3 4         9 7 1
3       1 9 4      
4     6 3     4   9 Step 5: #4 is in Columns D & F: #4 MUST go in Cell E8
5 9   4   5   1   7
6     7 4 8 9 2    
7   9   5 7 3       Step 6: #9 is in Columns G & H: #9 MUST go in Cell I4
8 2 7   8 4     9 6      (cf #9 in Row 6 @ F6 excludes use of Cell I6)
9   8     6   7 1  
A B C D E F G H I
1   1 9   3   6 4   Step 7: Complete Column E: need #s 1 & 2…
2 3 4     2   9 7 1      #1 can't go in Cell E2 (cf #1 in Row 2 @ I2), so
3       1 9 4            #1 MUST go in Cell E4, & therefore #2 MUST go in Cell E2
4     6 3 1   4   9
5 9   4   5   1   7
6     7 4 8 9 2    
7   9   5 7 3      
8 2 7   8 4     9 6
9   8     6   7 1  
A B C D E F G H I
1   1 9   3   6 4   Step 8: #1 is in Columns D & E: #1 MUST go in Cell F8
2 3 4     2   9 7 1      (cf #1 in Row 9 @ H9 excludes use of Cell F9)
3       1 9 4      
4     6 3 1   4   9
5 9   4   5   1   7
6     7 4 8 9 2    
7   9   5 7 3      
8 2 7   8 4 1   9 6
9   8     6   7 1  
A B C D E F G H I
1   1 9   3   6 4   Step 9: Complete Block HH: need #s 2 & 9…
2 3 4     2   9 7 1      #9 can't go in Cell F9 (cf #9 in Column F @ F6), so
3       1 9 4            #9 MUST go in Cell D9, & therefore #2 MUST go in Cell F9
4     6 3 1   4   9
5 9   4 2 5   1   7 Step 10: Now #2 is in Columns E & F: #2 MUST go in Cell D5
6     7 4 8 9 2    
7   9   5 7 3      
8 2 7   8 4 1   9 6
9   8   9 6 2 7 1  
A B C D E F G H I
1   1 9 7 3   6 4   Step 11: Complete Block EE: need #s 6 & 7…
2 3 4     2   9 7 1      #6 can't go in Cell F4 (cf #6 in Row 4 @ C4), so
3       1 9 4            #6 MUST go in Cell F5, & therefore #7 MUST go in Cell F4
4     6 3 1 7 4   9
5 9   4 2 5 6 1   7 Step 12: Now #7 is in Columns E & F: #7 MUST go in Cell D1
6     7 4 8 9 2          (cf #7 in Row 2 @ H2 excludes use of Cell D2)
7   9   5 7 3      
8 2 7   8 4 1   9 6
9   8   9 6 2 7 1  
A B C D E F G H I
1   1 9 7 3   6 4   Step 13: Complete Column D: #6 MUST go in Cell D2
2 3 4   6 2   9 7 1
3       1 9 4      
4     6 3 1 7 4   9 Step 14: Complete Row 5: need #s 3 & 8…
5 9 3 4 2 5 6 1 8 7      #8 can't go in Cell B5 (cf #8 in Column B @ B9), so
6     7 4 8 9 2          #8 MUST go in Cell H5, & therefore #3 MUST go in Cell B5
7   9   5 7 3      
8 2 7   8 4 1   9 6
9   8   9 6 2 7 1  
A B C D E F G H I
1   1 9 7 3   6 4   Step 15: Row 4 needs #8: #8 MUST go in Cell A4
2 3 4   6 2   9 7 1      (cf #8 in Column B @ B9 excludes use of Cell B4, &
3 7     1 9 4              #8 in Column H @ H5 excludes use of Cell H4)
4 8   6 3 1 7 4   9
5 9 3 4 2 5 6 1 8 7 Step 16: #7 is in Rows 1 & 2: #7 MUST go in Cell A3
6     7 4 8 9 2          (#7 in Column B @ B8 excludes use of Cell B3, &
7   9   5 7 3              #7 in Column C @ C6 excludes use of Cell C3)
8 2 7   8 4 1   9 6
9   8   9 6 2 7 1  
A B C D E F G H I
1   1 9 7 3   6 4   Step 17: Block DD needs #1: #1 MUST go in Cell A6
2 3 4   6 2   9 7 1      (cf #1 in Column B @ B1 excludes use of Cells B4 & B6)
3 7     1 9 4      
4 8   6