4 6
 2 4
 1 3
 3 5
 3 2
 6 3

What is the sum of the numbers missing from this Sudoku puzzle?

1. Don’t solve this Sudoku puzzle yet.

2. Add up the numbers you can see in the Sudoku grid.

3. Calculate the sum of the numbers that would be in the completed puzzle.

4. Calculate the sum of the numbers that are missing.

5. Finally complete the puzzle to see if your answers to 3 and 4 were correct.

• Transum,
•
• If you are not familiar with Sudoku it is a logic placement puzzle. It is normally presented in a 9×9 grid but the puzzle above is a smaller easier version.

The objective is to fill the grid so that each column, each row, and each of the six 2x3 boxes contains the digits from 1 to 6. Some of the numbers have already been placed ln the grid.
• The Best Maths Class Ever 7cd/m2, King Alfred's College, Oxfordshire
•
• We all started filling in the missing numbers. But realised that we could take the total of the numbers away from 21x6 to get the answer.
• ILB, Derbyshire
•
• Brilliant - I love the way that this gets people to use their thinking skills. I will definitely include this in my planning for next term.
• M Phillips, Ferndown
•
• Hi,
Great idea.
Good for deduction skills.
Would have been better if there had been only one solution. Current model leaves guesswork needed in places.

[Transum: Hello M Phillips: There's no guesswork required. There is one and only one unique solution (see comment from King Alfred's College above)]
• Mr Kavanagh's Fifth Class, Cork, Ireland
•
• We enjoyed this puzzle and had a follow on discussion about why people in Cork, Ireland all pronounce the game as Soduko instead of Sodoku.

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.

Previous Day | This starter is for 22 April | Next Day

The sum of the missing numbers is 77

You did not need to complete the sudoku puzzle to find this answer. The completed puzzle could look like this (though there might be other solutions).

 4 5 1 3 6 2
 3 2 6 4 5 1
 1 3 5 2 4 6
 6 4 2 1 3 5
 5 1 3 6 2 4
 2 6 4 5 1 3

Note to teacher: Doing this activity once with a class helps students develop strategies. It is only when they do this activity a second time that they will have the opportunity to practise those strategies. That is when the learning is consolidated. Click the button above to regenerate another version of this starter from random numbers.

Here is the URL which will take them to an interactive Sudoku activity.

Transum.org/go/?to=Sudoku

Here is the URL which will take them to similar number puzzles called Suko and Sujiko.

Transum.org/go/?to=Suko

For Students:

For All: