Some copies of Mastering Sudoku contain a misprint in
sample puzzle no. 30 (page 121). Here are the details:
Sample puzzle no. 30 should look like this:
but in some copies it's printed like this:
i.e. with the 2 in the bottom row in column 6 instead of column
5. The solution (page 170) is correct in all copies, and the puzzle is correct
in the Mastering Sudoku Gallery on this website.
(Click here to load the puzzle into SudokuXP or Sudoku@paulspages. Tip)
Please accept our apologies for this misprint. Here's a bonus
puzzle which will test your forcing pattern skills some more:
no. 53. Rating: Extreme
Like puzzle 30, this one seems to be cruising to an easy finish with just
basic solving techniques and a couple of claims - then suddenly it's gridlock.
You can either complete it with a forcing loop and
a forcing chain, or
you can try the XY-chain technique described in the Mastering
Sudoku readers' pages
The forcing loop has a whopping nine squares, and begins in the top three boxes.
The forcing chain also has nine squares - and you'll be in very familiar
territory when you find it!
Or try the XY-chain (a 'lite' version of a forcing
chain) - you could save a lot of time!
(Click here to load this puzzle into SudokuXP or Sudoku@paulspages. Tip)
Novice time: N/A
Improver time: 60 minutes
Expert time: 28 minutes