The most simple scanning technique is counting – select a row, column or region, and count the numbers in the cells in from 1 to 9, to identify the missing numbers.

Of course, this is most helpful when there is only one number missing from the row, column or region that you’re counting – then you know that number belongs in the missing blank cell.

Another counting technique is to select a blank cell, and work   …Read more

The more difficult Sudoku puzzles can’t be solved just by using the scanning techniques of crosshatching and counting. In these more complicated puzzles, scanning will still leave you with cells where you don’t know which of two or more numbers to choose.

These puzzles will require some more detailed analysis, and most people will need to do some marking up in order to make this analysis possible – very few people can remember all of the   …Read more