geometry
posted by shelby .
A lot is in the shape of a trapezoid. The sum of the bases is 180 feet. If the area of the lot is 8,100 square feet, what is the distance across the lot, i.e., the altitude of the figure?

http://www.mathopenref.com/trapezoidarea.html
a = h(b1 + b2)/2
8100 = 90h
8100/90 = h
90 = h 
Find the area of the following circle.
r = 9 yd.