Step 0

Starting puzzle

1 2 3 4 5 6 7 8 9
A                  
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6     7     8 4
F       6 3   5    
G 5     7     1 3  
H         5   9   6
I                  

Step 1

The number 3 does not yet appear in row E. Due to other 3s on the grid, the only place it can go is cell E7.

1 2 3 4 5 6 7 8 9
A                  
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6     7   3 8 4
F       6 3   5    
G 5     7     1 3  
H         5   9   6
I                  

Step 2

The number 6 does not yet appear in column 1. Due to other 6s on the grid, the only place it can go is cell I1.

1 2 3 4 5 6 7 8 9
A                  
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6     7   3 8 4
F       6 3   5    
G 5     7     1 3  
H         5   9   6
I 6                

Step 3

Because of the number 6 just placed, the only position in row G for another 6 is cell G5.

1 2 3 4 5 6 7 8 9
A                  
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6     7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H         5   9   6
I 6                

Step 4

The number 8 does not yet appear in column 7. Due to other 8s on the grid, the only place it can go is cell I7.

1 2 3 4 5 6 7 8 9
A                  
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6     7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H         5   9   6
I 6           8    

Step 5

The number 2 is missing from row E and its only possible position is cell E3.

1 2 3 4 5 6 7 8 9
A                  
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H         5   9   6
I 6           8    

Step 6

Because of the number 2 just placed, the only position in column 1 for another 2 is cell H1.

1 2 3 4 5 6 7 8 9
A                  
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H 2       5   9   6
I 6           8    

Step 7

The number 8 is missing from column 5 and its only possible position is cell A5.

1 2 3 4 5 6 7 8 9
A         8        
B 1   6   9        
C   2 9     6     8
D     3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H 2       5   9   6
I 6           8    

Step 8

Because of the number 8 just placed, the only position in row B for another 8 is cell B2.

1 2 3 4 5 6 7 8 9
A         8        
B 1 8 6   9        
C   2 9     6     8
D     3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H 2       5   9   6
I 6           8    

Step 9

The number 5 is missing from box D1-F3 and its only possible position is cell D2.

1 2 3 4 5 6 7 8 9
A         8        
B 1 8 6   9        
C   2 9     6     8
D   5 3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H 2       5   9   6
I 6           8    

Step 10

Because of the number 5 just placed, the only position in column 3 for another 5 is cell A3.

1 2 3 4 5 6 7 8 9
A     5   8        
B 1 8 6   9        
C   2 9     6     8
D   5 3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5    
G 5     7 6   1 3  
H 2       5   9   6
I 6           8    

Step 11

Cell G9 can only contain the number 2 since all other numbers are somewhere in its row, column or box.

1 2 3 4 5 6 7 8 9
A     5   8        
B 1 8 6   9        
C   2 9     6     8
D   5 3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5    
G 5     7 6   1 3 2
H 2       5   9   6
I 6           8    

Step 12

The number 2 does not yet appear in row F. Due to other 2s on the grid, the only place it can go is cell F8.

1 2 3 4 5 6 7 8 9
A     5   8        
B 1 8 6   9        
C   2 9     6     8
D   5 3   2 4      
E 9 6 2   7   3 8 4
F       6 3   5 2  
G 5     7 6   1 3 2
H 2       5   9   6
I 6           8    

Step 13

In row E, the missing 1 can only go in cell E4 or E6. All of these cells are in box D4-F6. Therefore 1 can be eliminated from other cells in box D4-F6 including D4, F6. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A     5   8        
B 1 8 6   9        
C   2 9     6     8
D   5 3 89 2 4      
E 9 6 2   7   3 8 4
F       6 3 89 5 2  
G 5     7 6   1 3 2
H 2       5   9   6
I 6           8    

Step 14

In box G7-I9, the missing 4 can only go in cell H8 or I8. All of these cells are in column 8. Therefore 4 can be eliminated from other cells in column 8 including A8, B8, C8. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A     5   8     1679  
B 1 8 6   9     57  
C   2 9     6   157 8
D   5 3 89 2 4      
E 9 6 2   7   3 8 4
F       6 3 89 5 2  
G 5     7 6   1 3 2
H 2       5   9   6
I 6           8    

Step 15

In row G, the missing 4 can only go in cell G2 or G3. All of these cells are in box G1-I3. Therefore 4 can be eliminated from other cells in box G1-I3 including H2, I2, H3, I3. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A     5   8     1679  
B 1 8 6   9     57  
C   2 9     6   157 8
D   5 3 89 2 4      
E 9 6 2   7   3 8 4
F       6 3 89 5 2  
G 5     7 6   1 3 2
H 2 137 178   5   9   6
I 6 1379 17       8    

Step 16

In box D1-F3, the missing 1 can only go in cell F2 or F3. All of these cells are in row F. Therefore 1 can be eliminated from other cells in row F including F9. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A     5   8     1679  
B 1 8 6   9     57  
C   2 9     6   157 8
D   5 3 89 2 4      
E 9 6 2   7   3 8 4
F       6 3 89 5 2 79
G 5     7 6   1 3 2
H 2 137 178   5   9   6
I 6 1379 17       8    

Step 17

In column 1, the missing 3 can only go in cell A1 or C1. All of these cells are in box A1-C3. Therefore 3 can be eliminated from other cells in box A1-C3 including A2. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A   47 5   8     1679  
B 1 8 6   9     57  
C   2 9     6   157 8
D   5 3 89 2 4      
E 9 6 2   7   3 8 4
F       6 3 89 5 2 79
G 5     7 6   1 3 2
H 2 137 178   5   9   6
I 6 1379 17       8    

Step 18

In column 1, the missing 8 can only go in cell D1 or F1. All of these cells are in box D1-F3. Therefore 8 can be eliminated from other cells in box D1-F3 including F3. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A   47 5   8     1679  
B 1 8 6   9     57  
C   2 9     6   157 8
D   5 3 89 2 4      
E 9 6 2   7   3 8 4
F     147 6 3 89 5 2 79
G 5     7 6   1 3 2
H 2 137 178   5   9   6
I 6 1379 17       8    

Step 19

In column 6, each of the cells F6 and G6 can only take one of the numbers 8 or 9. These 2 cells will use up these 2 numbers between them. Therefore the numbers can be eliminated from H6, I6 in column 6. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A   47 5   8     1679  
B 1 8 6   9     57  
C   2 9     6   157 8
D   5 3 89 2 4      
E 9 6 2   7   3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9   6
I 6 1379 17     123 8    

Step 20

In column 8, each of the cells B8 and H8 and I8 can only take one of the numbers 4 or 5 or 7. These 3 cells will use up these 3 numbers between them. Therefore the numbers can be eliminated from A8, C8, D8 in column 8. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A   47 5   8     169  
B 1 8 6   9     57  
C   2 9     6   1 8
D   5 3 89 2 4   169  
E 9 6 2   7   3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 21

The number 5 is missing from row C and its only possible position is cell C4.

1 2 3 4 5 6 7 8 9
A   47 5   8     169  
B 1 8 6   9     57  
C   2 9 5   6   1 8
D   5 3 89 2 4   169  
E 9 6 2   7   3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 22

Because of the number 5 just placed, the only position in column 6 for another 5 is cell E6.

1 2 3 4 5 6 7 8 9
A   47 5   8     169  
B 1 8 6   9     57  
C   2 9 5   6   1 8
D   5 3 89 2 4   169  
E 9 6 2   7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 23

E4 is the last empty cell in row E and the missing number is 1.

1 2 3 4 5 6 7 8 9
A   47 5   8     169  
B 1 8 6   9     57  
C   2 9 5   6   1 8
D   5 3 89 2 4   169  
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 24

The number 3 is missing from row C and its only possible position is cell C1.

1 2 3 4 5 6 7 8 9
A   47 5   8     169  
B 1 8 6   9     57  
C 3 2 9 5   6   1 8
D   5 3 89 2 4   169  
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 25

The number 7 is missing from row C and its only possible position is cell C7.

1 2 3 4 5 6 7 8 9
A   47 5   8     169  
B 1 8 6   9     5  
C 3 2 9 5   6 7 1 8
D   5 3 89 2 4   169  
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 26

The number 4 is missing from row C and its only possible position is cell C5.

1 2 3 4 5 6 7 8 9
A   47 5   8     169  
B 1 8 6   9     5  
C 3 2 9 5 4 6 7 1 8
D   5 3 89 2 4   169  
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 27

C8 is the last empty cell in row C and the missing number is 1.

1 2 3 4 5 6 7 8 9
A   47 5   8     69  
B 1 8 6   9     5  
C 3 2 9 5 4 6 7 1 8
D   5 3 89 2 4   69  
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 13 9 47 6
I 6 1379 17     123 8 457  

Step 28

Because of the number 1 just placed, the only position in row A for another 1 is cell A6.

1 2 3 4 5 6 7 8 9
A   47 5   8 1   69  
B 1 8 6   9     5  
C 3 2 9 5 4 6 7 1 8
D   5 3 89 2 4   69  
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 3 9 47 6
I 6 1379 17     23 8 457  

Step 29

I5 is the last empty cell in column 5 and the missing number is 1.

1 2 3 4 5 6 7 8 9
A   47 5   8 1   69  
B 1 8 6   9     5  
C 3 2 9 5 4 6 7 1 8
D   5 3 89 2 4   69  
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 3 9 47 6
I 6 379 7   1 23 8 457  

Step 30

Because of the number 1 just placed, the only position in column 9 for another 1 is cell D9.

1 2 3 4 5 6 7 8 9
A   47 5   8 1   69  
B 1 8 6   9     5  
C 3 2 9 5 4 6 7 1 8
D   5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 3 9 47 6
I 6 379 7   1 23 8 457  

Step 31

The number 7 does not yet appear in column 6. Due to other 7s on the grid, the only place it can go is cell B6.

1 2 3 4 5 6 7 8 9
A   47 5   8 1   69  
B 1 8 6   9 7   5  
C 3 2 9 5 4 6 7 1 8
D   5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F     147 6 3 89 5 2 79
G 5     7 6 89 1 3 2
H 2 137 178   5 3 9 47 6
I 6 379 7   1 23 8 457  

Step 32

The number 7 is missing from box D7-F9 and its only possible position is cell F9.

1 2 3 4 5 6 7 8 9
A   47 5   8 1   69  
B 1 8 6   9 7   5  
C 3 2 9 5 4 6 7 1 8
D   5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F     14 6 3 89 5 2 7
G 5     7 6 89 1 3 2
H 2 137 178   5 3 9 47 6
I 6 379 7   1 23 8 457  

Step 33

Because of the number 7 just placed, the only position in row D for another 7 is cell D1.

1 2 3 4 5 6 7 8 9
A   47 5   8 1   69  
B 1 8 6   9 7   5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F     14 6 3 89 5 2 7
G 5     7 6 89 1 3 2
H 2 137 178   5 3 9 47 6
I 6 379 7   1 23 8 457  

Step 34

The number 7 does not yet appear in row A. Due to other 7s on the grid, the only place it can go is cell A2.

1 2 3 4 5 6 7 8 9
A   7 5   8 1   69  
B 1 8 6   9 7   5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F     14 6 3 89 5 2 7
G 5     7 6 89 1 3 2
H 2 13 178   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 35

A1 is the last empty cell in box A1-C3 and the missing number is 4.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   69  
B 1 8 6   9 7   5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F     14 6 3 89 5 2 7
G 5     7 6 89 1 3 2
H 2 13 178   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 36

Because of the number 4 just placed, the only position in row B for another 4 is cell B7.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   69  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F     14 6 3 89 5 2 7
G 5     7 6 89 1 3 2
H 2 13 178   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 37

F1 is the last empty cell in column 1 and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   69  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 89 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5     7 6 89 1 3 2
H 2 13 178   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 38

Because of the number 8 just placed, the only position in row D for another 8 is cell D4.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   69  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5     7 6 89 1 3 2
H 2 13 178   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 39

Because of the number 8 just placed, the only position in column 6 for another 8 is cell G6.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   69  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5     7 6 8 1 3 2
H 2 13 178   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 40

Because of the number 8 just placed, the only position in column 3 for another 8 is cell H3.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   69  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5     7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 41

F6 is the last empty cell in box D4-F6 and the missing number is 9.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   69  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   69 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5     7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 42

Because of the number 9 just placed, the only position in row D for another 9 is cell D8.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   9 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5     7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 39 7   1 23 8 457  

Step 43

Because of the number 9 just placed, the only position in column 4 for another 9 is cell I4.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   9 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5     7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 44

Because of the number 9 just placed, the only position in row G for another 9 is cell G2.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6  
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   9 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5 9   7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 45

Because of the number 9 just placed, the only position in column 9 for another 9 is cell A9.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4   9 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5 9   7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 46

D7 is the last empty cell in box D7-F9 and the missing number is 6.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5 9   7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 47

Because of the number 6 just placed, the only position in column 8 for another 6 is cell A8.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8   14 6 3 9 5 2 7
G 5 9   7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 48

G3 is the last empty cell in row G and the missing number is 4.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8   1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 49

Because of the number 4 just placed, the only position in column 2 for another 4 is cell F2.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 50

F3 is the last empty cell in box D1-F3 and the missing number is 1.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 13 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 51

Because of the number 1 just placed, the only position in column 2 for another 1 is cell H2.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 47 6
I 6 3 7 9 1 23 8 457  

Step 52

I2 is the last empty cell in column 2 and the missing number is 3.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 47 6
I 6 3 7 9 1 2 8 457  

Step 53

I3 is the last empty cell in box G1-I3 and the missing number is 7.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 47 6
I 6 3 7 9 1 2 8 45  

Step 54

Because of the number 7 just placed, the only position in row H for another 7 is cell H8.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1   6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 45  

Step 55

A7 is the last empty cell in column 7 and the missing number is 2.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1 2 6 9
B 1 8 6   9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 45  

Step 56

Because of the number 2 just placed, the only position in row B for another 2 is cell B4.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1 2 6 9
B 1 8 6 2 9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 45  

Step 57

Because of the number 2 just placed, the only position in column 6 for another 2 is cell I6.

1 2 3 4 5 6 7 8 9
A 4 7 5   8 1 2 6 9
B 1 8 6 2 9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 45  

Step 58

A4 is the last empty cell in box A4-C6 and the missing number is 3.

1 2 3 4 5 6 7 8 9
A 4 7 5 3 8 1 2 6 9
B 1 8 6 2 9 7 4 5  
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 45  

Step 59

Because of the number 3 just placed, the only position in row B for another 3 is cell B9.

1 2 3 4 5 6 7 8 9
A 4 7 5 3 8 1 2 6 9
B 1 8 6 2 9 7 4 5 3
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 45  

Step 60

H6 is the last empty cell in column 6 and the missing number is 3.

1 2 3 4 5 6 7 8 9
A 4 7 5 3 8 1 2 6 9
B 1 8 6 2 9 7 4 5 3
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 45  

Step 61

B8 is the last empty cell in box A7-C9 and the missing number is 5.

1 2 3 4 5 6 7 8 9
A 4 7 5 3 8 1 2 6 9
B 1 8 6 2 9 7 4 5 3
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 4  

Step 62

I9 is the last empty cell in column 9 and the missing number is 5.

1 2 3 4 5 6 7 8 9
A 4 7 5 3 8 1 2 6 9
B 1 8 6 2 9 7 4 5 3
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8   5 3 9 7 6
I 6 3 7 9 1 2 8 4 5

Step 63

H4 is the last empty cell in box G4-I6 and the missing number is 4.

1 2 3 4 5 6 7 8 9
A 4 7 5 3 8 1 2 6 9
B 1 8 6 2 9 7 4 5 3
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8 4 5 3 9 7 6
I 6 3 7 9 1 2 8 4 5

Step 64

I8 is the last empty cell in row I and the missing number is 4.

Congratulations - the puzzle is solved!

1 2 3 4 5 6 7 8 9
A 4 7 5 3 8 1 2 6 9
B 1 8 6 2 9 7 4 5 3
C 3 2 9 5 4 6 7 1 8
D 7 5 3 8 2 4 6 9 1
E 9 6 2 1 7 5 3 8 4
F 8 4 1 6 3 9 5 2 7
G 5 9 4 7 6 8 1 3 2
H 2 1 8 4 5 3 9 7 6
I 6 3 7 9 1 2 8 4 5
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