Killer Sudoku: The rules of Killer Sudoku are almost the same as regular Sudoku: Each line must include all the numbers 1-9 with no repeats. And each box must also have all the numbers 1-9 with no repeats. Killer Sudoku is different because you don’t get any numbers to start you off. Instead you get dotted lines (‘cages’) around groups of boxes with a small number in their corners. The numbers inside the cage must add up to the number in the corner, and no repeats. Diabolical!
Alice Jones’ Top Tips for solving a Killer Sudoku
- Start small
- Since you don’t have any numbers to start with, look for cages with only one possible solution. For example: A cage that covers three cells with a 24 in the corner has to be made of 9,8 and 7. There’s no other way to get to 24. A three cell cage with a 6 in the corner has to be made of 1, 2 and 3. A two cell cage with a seventeen in the corner must be 8 and 9. And so on.
- 45 is the magic number
- Since 1+2+3+4+5+6+7+8+9=45, you know that each row (and each square) has to add up to 45.
- If you have a square with three cages and one free square add up the cage values and subtract it from 45 and PRESTO you’ve got the value of the free square! (this works for lines as well)
- Basic Sudoku rules apply
- Once you start filling in numbers, you can use the basic Sudoku rules to help fill in the grid. No number can appear twice in the same line or 3×3 box. For example: if you’ve got a cage of two cells with a 5 in the corner you know it could contain a 1 and a 4 OR a 2 and a 3. BUT if you already have a 3 in that box, then you know it’s got to be the 1, 4 combination since you can’t have duplicates. (There are no repeats allowed in a cage either)
- Take Notes
- Killer Sudoku is all about elimination, whittling away all the numbers that DON’T belong until all your left with is the one that does. But with nine boxes of nine squares and nine possible numbers for each square there are A LOT of possibilities to remember. Make a note of all the numbers that might be in a box and erase them as you solve more squares.
- Keep Moving
- If you keep focusing on the same square you can get stuck and frustrated, if you’re having trouble figuring one cage out, move on to something else.
Killer Sudoku Puzzles for you to try: