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Consecutive Numbers
An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
Tea Cups
Place the 16 different combinations of cup/saucer in this 4 by 4 arrangement so that no row or column contains more than one cup or saucer of the same colour.
Counting on Letters
The letters of the word ABACUS have been arranged in the shape of a triangle. How many different ways can you find to read the word ABACUS from this triangular pattern?
Age 11 to 16
Challenge Level
by Henry Kwok
Twin A
Twin B
You can download a word
document containing both the sudoku grids here.
Rules of Twin Corresponding Sudokus
The object of this sudoku variant is to fill in the whole of each 9x9 grid with numbers 1 through 9 (one number per cell) so that each row, each column, and each of the nine 3x3 squares contain all the nine different numbers 1 through 9.
This Sudoku problem 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 corresponding values of the digits from one twin sudoku into the other.
For example, we can see that in r4c9, that is row 4 column 9, twin A contains the number 3 and twin B contains the number 8. This means that everywhere the number 3 appears in twin A, the number 8 should appear in the corresponding position in twin B and vice versa. This immediately gives you some more starting digits in each twin! It is not necessary for a number in one twin puzzle to be different from its corresponding counterpart in the other twin puzzle.
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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.