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'Seasonal Twin Sudokus' printed from http://nrich.maths.org/

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by Henry Kwok

Twin A


Grid A

Twin B


Grid B

Rules of Seasonal Twin Sudokus

Each row, each column and each of the nine 3x3 boxes in Twin A and Twin B contains the 9 elements - a total of 10 letters in Twin A and all the nine different numbers 1 to 9 in Twin B.

This version of Sudoku consists of a pair of linked standard Sudoku puzzles, with some letters and digits as starters in twin A and twin B respectively. 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 corresponding element of each cell from one twin Sudoku into the other.

So, for example we can see that in (9,1), that is row 9 column 1, Twin A contains the letter A and Twin B contains the number 9. This means that everywhere a letter A appears in twin A - a 9 appears in the corresponding position in twin B and vice versa.

This immediately generates some more elements in the cells of each twin!

Note that (4,3) in Twin A contains two letters (CH) instead of one. This is a deviation from the regular Wordoku which contains only one letter per square. This is the only way to squeeze more than 9 required letters into the 9x9 grid of Twin A to form two hidden words.

Can you guess or spot the two hidden words in Twin A?