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Easy Puzzle #27 - 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 6 5     4     9   Easy Puzzle #27 - October 27, 2005
2 2   4 6   9 3   1 Original puzzle as published © joe-ks.com
3   9 8       4    
4   2   4 6     7  
5 5 6   8   2   3 4
6   8 9   3 7 2 6  
7     6       5    
8 8   5 9   3 6   7
9   4     8     1  
A B C D E F G H I
1 6 5     4     9   Step 1: #6 is in Rows 1 & 2: #6 MUST go in Cell I3
2 2   4 6   9 3   1      (cf #6 in Column H @ H6 excludes use of Cell H3)
3   9 8       4   6
4   2   4 6     7  
5 5 6   8   2   3 4
6   8 9   3 7 2 6  
7     6       5     Step 2: #6 is in Rows 7 & 8: #6 MUST go in Cell F9
8 8   5 9   3 6   7      (cf #6 in Column D @ D2 excludes use of Cell D9)
9   4     8 6   1  
A B C D E F G H I
1 6 5     4   7 9   Step 3: #4 is in Columns B & C: #4 MUST go in Cell A6
2 2   4 6   9 3   1      (cf #4 in Row 4 @ D4 excludes use of Cell A4)
3   9 8       4   6
4   2   4 6     7   Step 4: #4 is in Columns D & E: #4 MUST go in Cell F7…
5 5 6   8   2   3 4
6 4 8 9   3 7 2 6  
7     6     4 5     Step 5: #7 is in Columns H & I: #7 MUST go in Cell G1…
8 8   5 9   3 6   7
9   4     8 6   1  
A B C D E F G H I
1 6 5     4 8 7 9   Step 6: #2 is in Columns A & B: #2 MUST go in Cell C9…
2 2   4 6   9 3   1
3   9 8       4   6 Step 7: #8 is in Columns D & E: #8 MUST go in Cell F1
4   2   4 6     7        (cf #8 in Row 3 @ C3 excludes use of Cell F3)
5 5 6   8   2   3 4
6 4 8 9   3 7 2 6   Step 8: #4 is in Columns G & I: #4 MUST go in Cell H8
7     6     4 5          (cf #4 in Row 7 @ F7 excludes use of Cell H7)
8 8   5 9   3 6 4 7
9   4 2   8 6   1  
A B C D E F G H I
1 6 5     4 8 7 9   Step 9: Complete Row 6: need #s 1 & 5…
2 2   4 6   9 3   1      #1 can't go in Cell I6 (cf #1 in Column I @ I2), so
3   9 8       4   6      #1 MUST go in Cell D6, & therefore #5 MUST go in Cell I6
4   2   4 6     7  
5 5 6   8   2   3 4
6 4 8 9 1 3 7 2 6 5
7     6     4 5     Step 10: #5 is in Rows 7 & 8: #5 MUST go in Cell D9...
8 8   5 9   3 6 4 7
9   4 2 5 8 6   1  
A B C D E F G H I
1 6 5 1   4 8 7 9   Step 11: Complete Block EE: need #s 5 & 9…
2 2   4 6   9 3   1      #9 can't go in Cell F4 (cf #9 in Column F @ F2), so
3   9 8       4   6      #9 MUST go in Cell E5, & therefore #5 MUST go in Cell F4
4   2   4 6 5   7  
5 5 6   8 9 2   3 4 Step 12: Row 1 needs #1: #1 MUST go in Cell C1
6 4 8 9 1 3 7 2 6 5      (cf #1 in Column D @ D6 excludes use of Cell D1, &
7     6     4 5            #1 in Column I @ I2 excludes use of Cell I1)
8 8   5 9   3 6 4 7
9   4 2 5 8 6   1  
A B C D E F G H I
1 6 5 1   4 8 7 9   Step 13: #8 is in Rows 1 & 3: #8 MUST go in Cell H2…
2 2   4 6   9 3 8 1
3   9 8       4   6
4   2   4 6 5   7   Step 14: Block DD needs #7: #7 MUST go in Cell C5
5 5 6 7 8 9 2   3 4      (cf #7 in Row 4 @ H4 excludes use of Cells A4 & C4)
6 4 8 9 1 3 7 2 6 5
7     6     4 5   8 Step 15: #8 is in Rows 8 & 9: #8 MUST go in Cell I7
8 8   5 9   3 6 4 7      (cf #8 from Step13 @ H2 excludes use of Cell H7)
9   4 2 5 8 6   1  
A B C D E F G H I
1 6 5 1   4 8 7 9   Step 16: Complete Column C: #3 MUST go in Cell C4…
2 2   4 6   9 3 8 1
3   9 8     1 4   6
4   2 3 4 6 5   7   Step 17: Complete Column F: #1 MUST go in Cell F3…
5 5 6 7 8 9 2   3 4
6 4 8 9 1 3 7 2 6 5
7     6     4 5   8
8 8   5 9   3 6 4 7
9   4 2 5 8 6   1  
A B C D E F G H I
1 6 5 1   4 8 7 9 2 Step 18: Complete Block CC: need #s 2 & 5…
2 2   4 6   9 3 8 1      #5 can't go in Cell I1 (cf #5 in Row 1 @ B5), so
3   9 8     1 4 5 6      #5 MUST go in Cell H3, & therefore #2 MUST go in Cell I1
4   2 3 4 6 5   7  
5 5 6 7 8 9 2 1 3 4 Step 19: Complete Row 5: #1 MUST go in Cell G5…
6 4 8 9 1 3 7 2 6 5
7     6     4 5   8 Step 20: Row 9 needs #7: #7 MUST go in Cell A9
8 8   5 9   3 6 4 7      (cf #7 in Column G @ G1 excludes use of Cell G9, &
9 7 4 2 5 8 6   1          #7 in Column I @ I8 excludes use of Cell I9)
A B C D E F G H I
1 6 5 1 3 4 8 7 9 2 Step 21: Complete Row 1: #3 MUST go in Cell D1...
2 2   4 6   9 3 8 1
3   9 8     1 4 5 6
4   2 3 4 6 5 8 7   Step 22: Complete Column G: need #s 8 & 9…
5 5 6 7 8 9 2 1 3 4      #8 can't go in Cell G9 (cf #8 in Row 9 @ E9), so
6 4 8 9 1 3 7 2 6 5      #8 MUST go in Cell G4, & therefore #9 MUST go in Cell G9
7     6     4 5   8
8 8   5 9   3 6 4 7
9 7 4 2 5 8 6 9 1  
A B C D E F G H I
1 6 5 1 3 4 8 7 9 2 Step 23: Complete Block DD: #1 MUST go in Cell A4...
2 2   4 6   9 3 8 1
3   9 8     1 4 5 6
4 1 2 3 4 6 5 8 7 9 Step 24: Complete Block FF: #9 MUST go in Cell I4…
5 5 6