Small-group support
A triangle is half of a related parallelogram.
Find the area of the triangle.
Stopping before dividing counts the parallelogram. The height is perpendicular to the base. A slanted side is a length of the boundary, not the height, unless the figure is a rectangle.
Problem 1 of 4. A short entry task, a model, guided examples, then a new independent try. Frames are optional.