The first pair we spot is an obvious pair in row 1. Can you spot any pairs or triplets in Example #42.4? We will begin with Step 1, identifying Pairs, Triplets & Quads. Once you fill in the options for the unsolved cells, your grid should look like Example #42.4 below: Example #42.4 STEPS 1-8 Now your grid should look like Example #42.3 below: Example #42.3 Example #42.3 FILL IN THE OPTIONS FOR THE UNSOLVED CELLS … In box 4 a 7 can only exist in C1R5, C2R5 or C3R5 therefore, a 7 cannot exist in C5R5. In box 3 a 6 can only exist in C7R1 or C8R1 therefore, a 6 cannot exist in C4R1, C5R1 or C6R1. Pencil a small 4 in the bottom of those two cells to indicate they cannot be a 4. In box 4 a 4 can exist only in C1R5, C2R5 or C3R5 therefore, a 4 cannot exist as an option in C7R5 or C9R5. Now your grid should look like Example #42.2 below: Example #42.2 MARK UNSOLVED CELLS WITH OPTIONS THAT CANNOT EXIST IN THOSE CELLS … This leaves only one cell in box 9 that can be a 9. The only cells in box 7 that can be a 9 are C2R9 or C3R9 therefore, C7R9 & C9R9 cannot be a 9. This leaves only one cell in box 9 that can be a 3. The only cells in box 6 (right center box of 3x3 cells) that can be a 3 are C9R5 & C9R6 therefore, C9R9 cannot be a 3. Now your grid should look like Example #42.1 below: Example #42.1 NOT-SO-OBVIOUS ANSWERS … The first obvious answer is C8R5=2 (cell in column 8, row 5). Start with the 1’s to see if there are any obvious 1-choice answers.
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