Identify \(\text{every}~\text{card}\) whose area can be found by multiplying a base and corresponding height directly, without dividing by \(2\) or averaging \(\text{two}~\text{bases}\).
Card 1: a rectangle with side lengths \(9\) units and \(4\) units
Card 2: a triangle with base \(12\) units and height \(6\) units
Card 3: a parallelogram with base \(8\) units and height \(4.5\) units
Card 4: a trapezoid with bases \(10\) units and \(8\) units and height \(4\) units
Card 5: a composite figure made from a \(4\text{-}by-5\) rectangle and a right triangle with base \(4\) units and height \(8\) units
Card 6: a rectangle with side lengths \(6\) units and \(6\) units
Card 7: a triangular banner with base \(9\) units and height \(8\) units
Card 8: a parallelogram with base \(12\) units and height \(3\) units
What this problem is really about
Classify each region by the structure of its area formula, not merely by whether base and height appear. Rectangles and parallelograms use one direct product of a base and its corresponding perpendicular height; triangles add a one-half factor, trapezoids average two bases, and composites require multiple pieces. Test every card against that exact rule.