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The 45 Rule An essential Killer Sudoku solving technique is the "45 rule". This uses the fact that every row, column and block must contain each of the numbers 1 to 9 once. Therefore, the total of all numbers in one row, column or block will always be 45.

A three-by-three Sudoku puzzle will take between 10 to 30 minutes to complete depending on your skill and expertise and the difficulty of the puzzle. Four-by-four Sudoku puzzles will take much longer to complete. As these puzzles are much larger than three-by-three puzzles, they usually take upwards of two hours.

Sudoku is a daily puzzle game that can be played with or without a subscription. Here you can select your puzzle difficulty (easy, medium or hard). If you prefer a puzzle type you can go directly to those puzzles by using the links provided: Easy: nytimes.com/puzzles/sudoku/easy.

How to Play Daily Sudoku. The classic game of Sudoku challenges you to fill in a 9x9 grid with the numbers 1 through 9 without repeating a number in any row, column, or 3x3 box. Some numbers have already been filled in to help you get started, but it is up to you to solve the puzzle!

The most basic strategy to solve a Sudoku puzzle is to first write down, in each empty cell, all possible entries that will not contradict the One Rule with respect to the given cells. If a cell ends up having only one possible entry, it is a "forced" entry that you should fill in.

3 Sudoku types (Easy, Medium, and Hard) are released daily: Sunday–Thursday at 10 p.m. E.T.; Friday–Saturday at 6 p.m. E.T.

It's a peculiar name but a very fun, challenging little game. Numbword was developed by a two-person team in Turkey after one of the members was challenged by a friend to come up with an addictive puzzle game. It combines the 5-letter word guessing of Wordle with the number-puzzling of Sudoku.