Step-by-Step Solution

for Friday 20th December Diabolical

Number 8 is the only value possible in cell (4,1).

Single Candidate

For row 3, number 9 is only possible in cell (5,3)

Single Position

For row 9, number 9 is only possible in cell (8,9)

Single Position

For row 5, number 9 is only possible in cell (9,5)

Single Position

For row 7, number 9 is only possible in cell (3,7)

Single Position

For column 8, Number 8 is only possible in cell (8,7)

Single Position

For row 2, number 6 is only possible in cell (1,2)

Single Position

For row 7, number 6 is only possible in cell (5,7)

Single Position

For row 3, number 5 is only possible in cell (9,3)

Single Position

For column 4, Number 5 is only possible in cell (4,9)

Single Position

For column 4, Number 3 is only possible in cell (4,5)

Single Position

For column 5, Number 3 is only possible in cell (5,8)

Single Position

For column 6, Number 1 is only possible in cell (6,5)

Single Position

For column 5, Number 2 is only possible in cell (5,2)

Single Position

Number 7 is the only value possible in cell (6,1).

Single Candidate

For row 2, number 7 is only possible in cell (8,2)

Single Position

For box 7, candidates for 1 are all in column 2, so you can remove candidates from other blocks.

Candidate Lines

Candidates for 7 in boxes 5 and 6 force the candidates in box 4 to be in the remaining line.

Multiple Lines

Number 1 is the only value possible in cell (3,4).

Single Candidate

Number 8 is the only value possible in cell (3,6).

Single Candidate

Number 7 is the only value possible in cell (3,3).

Single Candidate

Naked Quad for 2,3,4 and 8, can remove these as candidates from other cells.

Naked Quads

Either candidate for cell (1,5) forces 3 into cell (2,6).

Forcing Chains

Number 2 is the only value possible in cell (2,1).

Single Candidate

Number 3 is the only value possible in cell (8,1).

Single Candidate

Number 8 is the only value possible in cell (2,3).

Single Candidate

Number 3 is the only value possible in cell (1,3).

Single Candidate

Number 4 is the only value possible in cell (2,9).

Single Candidate

Number 5 is the only value possible in cell (1,7).

Single Candidate

Number 4 is the only value possible in cell (1,4).

Single Candidate

Number 7 is the only value possible in cell (5,4).

Single Candidate

Number 3 is the only value possible in cell (7,4).

Single Candidate

Number 6 is the only value possible in cell (8,4).

Single Candidate

Number 5 is the only value possible in cell (2,4).

Single Candidate

Number 7 is the only value possible in cell (1,5).

Single Candidate

Number 6 is the only value possible in cell (2,5).

Single Candidate

Number 4 is the only value possible in cell (8,5).

Single Candidate

Number 4 is the only value possible in cell (5,6).

Single Candidate

Number 1 is the only value possible in cell (2,7).

Single Candidate

Number 2 is the only value possible in cell (7,7).

Single Candidate

Number 1 is the only value possible in cell (7,3).

Single Candidate

Number 4 is the only value possible in cell (9,2).

Single Candidate

Number 1 is the only value possible in cell (4,2).

Single Candidate

Number 4 is the only value possible in cell (4,3).

Single Candidate

Number 2 is the only value possible in cell (8,3).

Single Candidate

Number 7 is the only value possible in cell (7,6).

Single Candidate

Number 1 is the only value possible in cell (8,6).

Single Candidate

Number 2 is the only value possible in cell (9,6).

Single Candidate

Number 4 is the only value possible in cell (6,7).

Single Candidate

Number 3 is the only value possible in cell (9,7).

Single Candidate

Number 8 is the only value possible in cell (1,8).

Single Candidate

Number 7 is the only value possible in cell (2,8).

Single Candidate

Number 2 is the only value possible in cell (6,8).

Single Candidate

Number 1 is the only value possible in cell (9,8).

Single Candidate

Number 8 is the only value possible in cell (6,9).

Single Candidate