You may also like

problem icon

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.

problem icon

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?

problem icon

Teddy Town

There are nine teddies in Teddy Town - three red, three blue and three yellow. There are also nine houses, three of each colour. Can you put them on the map of Teddy Town according to the rules?

Quadruple Sudoku

Stage: 3 and 4 Challenge Level: Challenge Level:2 Challenge Level:2
By Henry Kwok

Rules of Quadruple Sudoku

This is a variation of sudoku on a standard 9x9 grid. The object of the puzzle is to fill in the whole 9x9 grid with numbers 1 through 9 (one number per cell) so that each row, each column, and each of the nine 3x3 boxes contains all the nine different numbers 1 through 9.

The clues are in the form of sets of four special clue-numbers. Each set of four numbers can be foundat the intersection of two grid lines and they are the numbers in the four adjacent grid cell.

How the special clue numbers work:
Each set of four cells around four clue numbers overlaps an adjacent set of four cells around a separate set of clue numbers. The shared or overlapping cell must contain a digit that is in both of the small sets.

For example, the two sets ofsmall digits {1678} and {1249} in the top lefthand box of the grid both referencethe cell (2,2). This cell must therefore contain the digit 1 as it is the only digit common to the two sets of special clue numbers.