Math
posted by Joe .
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? The altitude of the trapezoid is __ feet.

(a+b)/2 * h = 8100
180/2 h = 8100
90h = 8100
h = 90