Mini-Sudoku
How many ways are there of completing the mini-sudoku?
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![Mini-Sudoku Mini-Sudoku](/sites/default/files/styles/large/public/thumbnails/content-id-10156-wp8%2525202015%252520new.png?itok=emI7OxL9)
A mini-sudoku is a 4 by 4 grid, where each row, column and 2 by 2 outlined block contains the digits 1, 2, 3 and 4 once and once only.
How many different ways are there of completing the mini-sudoku shown?
If you liked this problem, here is an NRICH task that challenges you to use similar mathematical ideas.
The top 2 by 2 outlined block must contain a 3 and a 4, and this can be done in two ways. For each choice there is only one way to complete the entire mini-sudoku.