[tex] base: \ a= 26 \frac{2}{5} \ dm \\ base: \ b= 31\frac{2}{3}\ dm\\vertical \ height: \ h=20 \ dm \\ Trapezoids \ Area: \\\\A =\frac{1 }{2} (a+b) \cdot h\\\\A =\frac{1 }{2}\cdot ( 26\frac{2}{5} +31\frac{2}{3})\cdot 20= 10\cdot (26\frac{6}{15} +31\frac{10}{15})=10\cdot 57\frac{16}{15}=10\cdot 57\frac{16}{15}=\\\\=10\cdot \frac{871}{15}=\frac{1742}{3}=580\frac{2}{3}\ dm[/tex]
