Sudoku Tips and Tricks

This tip shows you how to criss-cross a single number to be able to enter it in a block.

In this video we will show you how to fill in the last empty field in a block.
Let’s look at the grid…each row, column and block must contain all numbers from 1-9. And the number 3 is already present in the row and column, which means there is only one field where number 3 can be put in this block, as the numbers can’t repeat.

The same logic applies to rows. Let’s look at the top row. There is no number 7 in the top row, but there are several number 7s in the columns and in the block above. If we know that the same number can’t appear more than once in the same row, column and block, we can conclude that the only place the number 7 can appear is HERE. Other fields in this row can’t contain the number 7 as it would then be repeated.

Now, let’s take a look at the far left column. The same rule as above applies here, too. The number 9 is missing on the column, but we have several 9s in other rows, and in the block. This means that number 9 can’t be used in THESE fields, and there is only one field where we can put 9. Other fields in this block can’t contain a 9 as the numbers in other rows prohibit it.

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