To find the surface of a figure we find the area of each face and sum them
then
Triangles
Area
[tex]\begin{gathered} A=\frac{b\times h}{2} \\ \\ A=\frac{20\times15}{2} \\ \\ A=150 \end{gathered}[/tex]
the area of one triangle is 150, the whole figure has 4 triangles, then the total area of the triangles face is
[tex]150\times4=600[/tex]
600 square feet
Squares
Area
[tex]\begin{gathered} A=l\times l \\ A=20\times20 \\ A=400 \end{gathered}[/tex]
area of a square is 400square feet, whole figure has 5 squares then
[tex]400\times5=2000[/tex]
the are of squares is 2000square feet
Total surface
we sum total area of the triangles an total area of the squares
[tex]600+2000=2600[/tex]
surface area of the figure is 2600square feet
