... by: Frans Goosens

#649

Combination 2-digits cells

B1=3 Wrong, Undo calculation
B1=5 No solution, Fixed
B2=3 Wrong, Undo calculation
B2=9 ( A2=1 ) Solved,

Total solving time is : 73 sec.
Number of logical steps is : 9771

... by: BGH

2 Step Solution after Basic Deterministics for #649
1. 7 @ E6 (Column 6 has Unit 7's in rows B & E, one of the two 7's is in the solution)
2. 6 @ F1 (16 pair in F1, Intersecting Triple Column 1, Quintuple in Row F, ripples from there)
--- One of the two digits is in the solution.

... by: Dieter

#649 - populated cells = 23 = 28,4%
basics: G9=4, J3=7, D6=8
populated cells = 26 = 32,1%
strategy: try to get hidden pairs or triplets. No solver used.
combinations of C4 = (2,4,7,9) and C5 = (4,8,9) as numbers 4,7,8 are populated most.
2 matrices left after basic checks: C4/C5 = (2/8) and (7/9)
start with C4/C5 = (7/9) as 50,6% populated: solves with F1=6

Review:
C5=9 & F1=6 or C4=7 & F1=6 solve.

... by: Serban

#649 D6=8 G9=4 J3=7 Basics to 26

1. Number 6 n=3 e=6 N=18 Nc=9 Ns=6 => F1=6 solve

1. Number 7 n=4 e=5 N=15 Nc=6 Ns=2 =>B9=7 basics to 44
2. XY-Wing 129 [H16,F6] => F1<>1 => F1=6 solve

1. Number 8 n=4 e=5 N=15 Nc=10 Ns=9 => A8=8 basics to 38
2. X-chain x=2 => [F1,H2,C4,E7,A9]<>2 => E2=F9=2 basics to 52
3. XY-Wing 129 [H16,F6] => F1<>1 => F1=6 solve