Colour islands Sudoku 2

In this Sudoku, there are three coloured "islands" in the 9x9 grid. Within each "island" EVERY group of nine cells that form a 3x3 square must contain the numbers 1 through 9.

Age
11 to 18
Challenge level
filled star empty star empty star
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

Problem



By Henry Kwok

 

Colour Islands Sudoku 2



 

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 boxes must contain all the nine different numbers 1 through 9.

There are three coloured "islands" in the 9x9 grid. Within each 'island' there is an extra rule to apply:

 

  • EVERY group of nine cells that form a 3x3 square within each 'island' must contain the numbers 1 through 9.

For example, take the cell r6c8 which contains the number 9 as the centre of a 3x3 square within the pink 'island'. The eight surrounding cells (r5c7, r5c8, r5c9, r6c7, r6c9, r7c7, r7c8 and r7c9) must contain all the remaining eight digits.