### 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?

# Colour Islands Sudoku

By Henry Kwok

#### Rules of Colour Islands Sudoku

As in a standard Sudoku, the object of the puzzle is to fill in the whole 9x9 grid with numbers 1 through 9 so that each row, each column, and each of the nine 3x3 squares must contain all the nine different numbers 1 through 9.

There are two coloured "islands" in the 9x9 grid. Within each "island" there are two extra rules to apply:
• no two diagonally adjacent cells can contain the same number
• EVERY 3x3 square within the islands must contain the numbers 1 through 9.
For example the cell (5,3) contains the number 5 so the cell (6,4) in the yellow island cannot contain a 5 because it is diagonally adjacent to (6,4) - being to the right and down one.
The 9x9 grid with corners at C4R3, C4R5, C6R5 and C6R3 must contain all the digits 1 to 9.