1. Look for scenarios where there is only one number missing from a group of four. In the example below, pupils should easily be able to work out that the missing digit (A) is 4, so that all four digits add together to make 21.

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2. Where there are two numbers missing, pupils should be able to work out the sum of the two missing numbers by taking away the numbers provided from the star. So, we know that the two missing  numbers B and C must add to 2 and 7 to make 16. Therefore B+C must equal 7. 

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3. Encourage pupils to find all possibilities. If we know that two numbers make 7, what could they be? (6+1, 5+2, 4+3). If any of these digits have already been used, we can eliminate them as options.  

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4. Use trial and error, especially in situations where one square has only two possibilities. If we assumed B equalled 6 and C equalled 1, what would happen elsewhere?  B+D must equal 10, (5+2=7), therefore D would need to be 4. However, E cannot be 7 (in order to make 28), as this number has already been used. Therefore, B cannot be 6. Using trial and error helps us to see the implications for certain choices, allowing us to quickly eliminate (or confirm!)

certain possibilities. With practice, these strategies should enable

many pupils to solve even the toughest of Sujiko.

Good luck!