The equation for the area of a trapezoid is [tex]A = \frac{1}{2}h(a+b)[/tex], where A=area, a & b = lengths of your bases (aka the parallel sides of your trapezoid), and h = height of the trapezoid.
The bases are 198 mi and 276 mi. I'm going to say a = 198 mi and b = 276 mi, but you can switch the values of the bases around, it won't affect your solution! The height, h = 270 mi. Plug these values into the equation for the area of a trapezoid and solve for A:
[tex]A = \frac{1}{2}h(a+b)\\
A = \frac{1}{2}(270\:mi)(198\:mi+276\:mi)\\
A = \frac{1}{2}(270\:mi)(474\:mi)\\
A = \frac{1}{2}(127980\:mi^{2})\\
A = 63990\:mi^{2}[/tex]
The estimated area of Missouri is [tex]A = 63990\:mi^{2}[/tex].
