The full reasoning can be found below the Sudoku.
May 07 - Hard
Puzzle Copyright © Kevin Stone
Reasoning
R1C6 can only be <2>
R1C4 can only be <7>
R2C4 can only be <9>
R1C5 can only be <4>
R5C5 is the only square in column 5 that can be <7>
R7C5 is the only square in column 5 that can be <2>
R8C6 is the only square in column 6 that can be <5>
R9C6 is the only square in column 6 that can be <9>
R9C2 can only be <7>
R8C2 can only be <9>
R8C1 can only be <3>
R8C7 can only be <2>
R8C9 can only be <7>
R6C3 is the only square in row 6 that can be <7>
R4C8 is the only square in row 4 that can be <7>
R4C3 is the only square in column 3 that can be <3>
R3C6 is the only square in column 6 that can be <3>
R3C5 can only be <1>
R9C5 can only be <3>
Squares R7C4 and R9C4 in column 4 form a simple naked pair. These 2 squares both contain the 2 possibilities <16>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.
R4C4 - removing <16> from <1268> leaving <28>
R6C4 - removing <16> from <1268> leaving <28>
Squares R1C7 and R4C7 in column 7 form a simple naked pair. These 2 squares both contain the 2 possibilities <56>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.
R3C7 - removing <6> from <469> leaving <49>
R6C7 - removing <6> from <369> leaving <39>
R7C7 - removing <6> from <346> leaving <34>
Intersection of column 3 with block 1. The value <2> only appears in one or more of squares R1C3, R2C3 and R3C3 of column 3. These squares are the ones that intersect with block 1. Thus, the other (non-intersecting) squares of block 1 cannot contain this value.
R3C2 - removing <2> from <268> leaving <68>
Intersection of column 3 with block 7. The value <1> only appears in one or more of squares R7C3, R8C3 and R9C3 of column 3. These squares are the ones that intersect with block 7. Thus, the other (non-intersecting) squares of block 7 cannot contain this value.
R7C1 - removing <1> from <1458> leaving <458>
Intersection of column 8 with block 3. The value <8> only appears in one or more of squares R1C8, R2C8 and R3C8 of column 8. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.
R3C9 - removing <8> from <2468> leaving <246>
Squares R2C1<45>, R2C3<245> and R3C3<24> in block 1 form a comprehensive naked triplet. These 3 squares can only contain the 3 possibilities <245>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.
R1C1 - removing <5> from <568> leaving <68>
R1C7 is the only square in row 1 that can be <5>
R4C7 can only be <6>
R4C6 can only be <1>
R4C1 can only be <5>
R6C6 can only be <6>
R6C2 can only be <2>
R2C1 can only be <4>
R6C4 can only be <8>
R5C2 can only be <6>
R6C9 can only be <3>
R4C4 can only be <2>
R6C7 can only be <9>
R2C9 can only be <2>
R7C1 can only be <8>
R3C3 can only be <2>
R2C3 can only be <5>
R2C8 can only be <3>
R4C9 can only be <8>
R5C9 can only be <5>
R5C1 can only be <9>
R3C2 can only be <8>
R6C1 can only be <1>
R3C7 can only be <4>
R5C8 can only be <2>
R7C2 can only be <5>
R1C1 can only be <6>
R1C8 can only be <8>
R7C8 can only be <6>
R3C9 can only be <6>
R7C7 can only be <3>
R3C8 can only be <9>
R9C9 can only be <4>
R7C4 can only be <1>
R9C3 can only be <1>
R7C3 can only be <4>
R9C4 can only be <6>
Today's Sudoku Puzzles
All daily items change at midnight GMT. set time zone