Area of triangles

Target: Find half of base times height.

Language target: Explain the half.

Likely miss: Students forget to take half, or they use a slanted side as the height.

Ask: What parallelogram is this triangle half of?

If you see it: Ask where the right angle of the height meets the base.

Evidence to listen for: The student multiplies base by perpendicular height.

Next: Sketch the height outside the figure if it falls outside.

Observable student moves: names both quantities, uses the represented relationship, and revises after feedback. This companion is not a score.