Notatii: L = lungime; l = latime; P = perimetru; A = aria.
[tex]l = \frac{5}{7}\cdot L \\ P=2L+2l=2(L+l)=2(L+ \frac{5}{7}\cdot L) \\ =2( \frac{7L}{7} + \frac{5L}{7})=2\cdot \frac{12L}{7}= \frac{24}{7}L=432\ cm \\ L= \frac{7\cdot432}{24}\ cm= 126\ cm. \\ l= \frac{5}{7}\cdot 126= 90. \\ Verificare: \\ 2(90+126)=2\cdot216=432cm \\ A=L\cdot l=126\cdot90=11340\ cm^2=1,134\ m^2.[/tex]
