ClipArt ETC
"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the trapezoid, and whose altitude is the same as that of the trapezoid." -Foster, 1921

Area of Trapezoid

"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the…

"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the trapezoid, and whose altitude is the same as that of the trapezoid." -Foster, 1921

Area of Trapezoid

"The student sees the trapezoid is equal in area to a rectangle whose base is the average base of the…