The full reasoning can be found below the Sudoku.
May 09 - Hard
Puzzle Copyright © Kevin Stone
Reasoning
R2C1 is the only square in row 2 that can be <8>
R2C5 is the only square in row 2 that can be <9>
R4C2 is the only square in row 4 that can be <9>
R1C3 is the only square in row 1 that can be <9>
R6C8 is the only square in row 6 that can be <6>
R6C2 is the only square in row 6 that can be <4>
R8C5 is the only square in row 8 that can be <3>
R8C1 is the only square in row 8 that can be <9>
R9C7 is the only square in row 9 that can be <9>
R9C8 is the only square in row 9 that can be <3>
R1C7 is the only square in row 1 that can be <3>
R1C2 is the only square in row 1 that can be <6>
R9C3 is the only square in row 9 that can be <6>
R6C4 is the only square in column 4 that can be <3>
R3C5 is the only square in column 5 that can be <6>
Squares R2C4 and R2C8 in row 2 form a simple naked pair. These 2 squares both contain the 2 possibilities <25>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.
R2C9 - removing <25> from <1256> leaving <16>
Squares R2C7 and R2C9 in block 3 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 block.
R3C7 - removing <1> from <147> leaving <47>
R3C9 - removing <1> from <1245> leaving <245>
Squares R7C1 and R8C3 in block 7 form a simple naked pair. These 2 squares both contain the 2 possibilities <57>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.
R7C3 - removing <57> from <1257> leaving <12>
R8C2 - removing <5> from <58> leaving <8>
R9C6 is the only square in row 9 that can be <8>
R6C5 is the only square in row 6 that can be <8>
R4C6 is the only square in column 6 that can be <1>
R4C4 is the only square in row 4 that can be <5>
R2C4 can only be <2>
R2C8 can only be <5>
R9C4 can only be <1>
R9C2 can only be <2>
R5C2 can only be <5>
R7C3 can only be <1>
R3C2 can only be <1>
R1C6 is the only square in row 1 that can be <5>
R3C9 is the only square in row 3 that can be <2>
R5C9 can only be <1>
R2C9 can only be <6>
R2C7 can only be <1>
R7C5 is the only square in row 7 that can be <2>
R4C5 can only be <7>
R4C7 can only be <4>
R6C6 can only be <2>
R4C8 can only be <2>
R3C7 can only be <7>
R6C3 can only be <7>
R3C6 can only be <4>
R5C7 can only be <8>
R1C8 can only be <4>
R5C8 can only be <7>
R7C7 can only be <6>
R5C1 can only be <3>
R8C3 can only be <5>
R8C9 can only be <4>
R3C3 can only be <3>
R7C1 can only be <7>
R8C6 can only be <7>
R7C9 can only be <5>
R7C8 can only be <8>
R1C4 can only be <7>
R3C1 can only be <5>
R5C3 can only be <2>
R7C4 can only be <4>
Today's Sudoku Puzzles
All daily items change at midnight GMT. set time zone