Students in Ms. Lyons's Math A (Math 6) class create a trapezoid (orange) on grid paper. They then make a copy of the the trapezoid (green), rotate it 180º, and place it next to the original trapezoid to create a parallelogram. At this point, they know that the area of a parallelogram is base x height. Asking them to generalize a formula to determine the area of the trapezoid, students see that the base of the the orange trapezoid (8 units) + the base of the green trapezoid (2 units) = the base of the new parallelogram (10 units). The height of the parallelogram is 5 units. So, the area of the parallelogram is
10 x 5 = 50 square units. The area of each of the trapezoids is 25 square units.

The students can generalize a formula for finding the area of a trapezoid:
h (b1 + b2) ÷ 2 = a

It is important for the students to determine the area of the figure by counting the squares, also, to check to see if the formula worked. This lesson also is a good review of rotations and determining area and perimeter. These students are in fourth grade, and many of the indicators in this Math 6 lesson review what they will be expected to know on the Maryland State Assessment. The teacher must also review with these students that when they are measuring area, they use square units. But when they are measuring perimeter, or simply the length of the base, they are measuring simply in units, something the students here confused.