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Guide and features
Science, Technology, Engineering and Mathematics
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Featured UK Key Stages 3 & 4; US Grade 5-10
Featured UK Key Stage 4 & 5; US Grade 11 & 12
Twin Corresponding Sudoku
Stage: 3, 4 and 5
By Henry Kwok
Rules of Twin Corresponding Sudoku
As with all the Sudoku puzzles published here, the object is to fill in the whole of each 9x9 grid with numbers 1 through 9 (one number per cell) so that each horizontal line, each vertical line, and each of the nine 3x3 squares (outlined with the bold lines) contain all the nine different numbers 1 through 9.
This problem is different because it consists of a pair of linked standard Sudoku puzzles each with some starting digits. To get a complete solution for the twin puzzles, we have to solve each twin puzzle with the usual strategies but we can only get the complete solution for the twin puzzles by substituting the equivalent values of the digits from one twin Sudoku into the other. So, for example, we can see that in (2,1), that is row 2 column 1, twin A contains the number 4 and twin B contains the number 7. This means that everywhere a 4 appears in twin A - a 7 appears in twin B and vice versa. This immediately gives you some more starting digits in each twin!
Meet the team
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities can be found here.
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