Draw this grid on the board or modelling book and give the students two or three minutes to write as many addition and subtraction equations as they can based around these digits.

 The numbers in the equation must be connected vertically, horizontally, or diagonally. For example, with this grid these are acceptable: 15 – 12 = 3,

5 + 7 = 12 (but not 7 + 5 = 12), 15 – 3 – 7 = 5.

Equations involve two or more numbers, and one or more operations, but no number can be used twice. The students compare their equations in groups. They gain points for each equation only they have recorded. One point is given for each number used in the equation, for example, 15 – 3 – 7 = 4 + 1 earns five points! The player with the most points wins.