Fie a-baza mică, b-baza mare
m-linia mijlocie
h-inaltimea
[tex] \left \{ {{\frac{a}{b}= \frac{3}{5}} \atop {\frac{a+b}{2}=m}} \right. [/tex][tex] \left \{ {{5a=3b} \atop { \frac{a+b}{2}=16 }} \right.
\left \{ {{a= \frac{3b}{5} } \atop {\frac{a+b}{2}=16}} \right.
\left \{ {{a= \frac{3b}{5} } \atop {\frac{ \frac{3b}{5}+b}{2}=16}} \right.
\left \{ {{a= \frac{3b}{5} } \atop {\frac{8b}{10}=16}} \right.
\left \{ {{a= \frac{3b}{5} } \atop {8b=160}} \right.
\left \{ {{a= \frac{3b}{5} } \atop {b=20}} \right.
\left \{ {{a= 12 } \atop {b=20}} \right.
[/tex]
Lungimile bazelor sunt: 12, 20
Aria trapezului este: m*h=16*8=128
