Strategies for Number Puzzles of all kinds
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Tuesday 19-Aug-2014

... by: JC


I built my own Sudoku Solver using C#, thanks for the challenge !

Monday 18-Aug-2014

... by: Ryan Wada

I used a non-Sudoku strategy and got 7 possibilities for 2 numbers.
When I tried F!=4 & F4=5, the solver did its job. Can you guess the strategy?

Saturday 5-Jul-2014

... by: sanjana

Hi ,
My mother in low is an avid user of this site , but unfortunately we are unable to open the puzzle on an IPAD . can you make sure it can be opened on IPAD ?

Saturday 5-Jul-2014

... by: JPF Naperville IL

Miss my unsolveable. Once again, how about a puzzle pack of puzzles
which still rate your unsolveable tag!

Wednesday 16-Apr-2014

... by: neo

My sudoku solver didn't have any problems with this one. A different program also tells me there is only one solution.

Friday 21-Mar-2014

... by: Mark7

1A1, 2E5, 3G5 leads to logical solution

Sunday 16-Mar-2014

... by: newby

using 2 (E4, E5) and 9 on row E;
6 (B4, C5) and 6 (D9, E9) against (1,3,4)F1 yields:
2E5, 9E4, 6E9, 6B4, 4F1 solves

Wednesday 12-Mar-2014

... by: ray

Billy Mac, please send me your system to:


Saturday 8-Mar-2014

... by: Billy Mac

I solved this puzzle, because I have been doing puzzles for about 10 years and I have diligently observed that there are 2-3 patterns that can be relied on to cancel numbers without seeing ahead of time the logical deduction. If you give me an email address I will send you the sequence of my entries, but I will not at this time reveal my patterns for elimination,
Sincerely, Billy Mac

Saturday 8-Mar-2014

... by: JC Van Hay

Re-Typo : read F1=4; UP30 :(

Saturday 8-Mar-2014

... by: JC Van Hay

Typo : read F1=1; UP30

Saturday 8-Mar-2014

... by: JC Van Hay

#1. All Cells Rank 0 Logic : the 15 cells ADFH1457-D1 are covered by the 15 sets 27RowA, 37RowD, 3RowF, 69RowH and 14Column1, 45Column4, 18Column5, 58Column7 :=> 24 eliminations : -27A29, -37D169, -3F8, -6H2 and -14DGJ1, -45BEG4, -18CEG5, -58CG7
:::. D1=6=F9, D7=7; UP24
:::. LC(3D45,3J89,6H45)-3EF45,3G789,6G45; Skyscraper(3BF1,3CF7)-3B89C2
:::. NT(135)E238-15E6; HT(568-1247)G23H2; NQ(2379)G1457-279G689; HT(237-1458)BCJ9
#2. F1=1or3->Contradiction(Singles) :=> F6=4; UP30

F1=1->A2=1,F4=4,F5=8,F7=3,F8=5=B6,C6=8,D6=1=H5,C5=6,B4=9,B8=8; Row A is devoid of 8 !
F1=3->F4=4,B2=3=E8=J9=C7,G7=2,H7=9,H4=6=B3,H5=1=D6,B6=5,F5=8=A7; Row B is devoid of 8 !

:::. ER(8F5=8F8-8BCB=8A79)-8A5; C6=8; UP31
:::. NP(27)A45-27A17B4C5; UP35
:::. UR(27)AE45=9E45-(9=7)E6; UP81

Saturday 8-Mar-2014

... by: ray

#1. Apply basic strategies and bi-location tool.
#2. Need to form, progressively, a 4-bi-location cell set E59G5J8. Forcing the various 4-cell values
gives inconclusions or contradictions untill E59G5J8 = (2,6,3,3) which gives the solution.
#3. Using this solution,with basic strategies, the following 2-cell solutions are found: GH4 = (7,4),
GH1 = (2,9), GJ1 = (2,7), D46 = 3,4), GJ6 = (1,9).

Saturday 8-Mar-2014

... by: newby

4H4, 3G4>contradiction
4H4, 3G5, 4D6, 4F1
6D9 inconclusive
6E9 solves


Each week a new 'unsolvable' will be published and the previous will be accessible here from this archive section. If you like very tough puzzles, these are for you.
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Page created on 03-May-2011, last modified on 03-May-2011.
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