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Students work with a given number of connecting cubes. They break the cubes into two parts and represent the parts and the total number of cubes on their recording sheets.
Connecting cubes
1 inch multifix cubes, often called linking cubes
What's Behind My Back Stage 1 Recording Sheet
Students begin with a tower of 5–10 connecting cubes. One student breaks the tower into two parts and shows the parts to their partner, who finds and states the number of cubes in the two parts. Each partner represents the two parts on their recording sheet by drawing or coloring the connecting cubes and writing an expression.
Connecting cubes
1 inch multifix cubes, often called linking cubes
What's Behind My Back Stage 2 Recording Sheet
Students begin with a tower of 10 cubes. One student breaks the tower into two parts, puts one part behind their back, and shows the other part to their partner, who figures out how many cubes are missing. Each partner represents the two parts on their recording sheet by drawing or coloring the connecting cubes and filling in an equation.
Connecting cubes
1 inch multifix cubes, often called linking cubes
What's Behind My Back Stage 3 Recording Sheet
Students begin with a tower of 10 connecting cubes. One student breaks the tower into two parts, puts one part behind their back, and shows the other part to their partner. The partner records an addition equation, with a blank to represent the unknown part, figures out how many cubes make up the unknown part, and then completes the equation.
Connecting cubes
1 inch multifix cubes, often called linking cubes
What's Behind My Back Stage 4 Recording Sheet
Students begin with 20 cubes, organized into two towers of 10 cubes. One student breaks the towers into two parts, puts one part of each tower behind their back, and shows the other parts to their partner. The partner records an addition equation, with a blank to represent the missing part, figures out how many cubes make up the missing part, and then completes the equation.
Each group of 2 students needs 2 towers of 10 connecting cubes.