3.
[tex]\it \mathcal{P}_{dreptunghi} =2(L+\ell)=2(9+7)=32cm\\ \\ \mathcal{P}_{p\breve atrat} =4\cdot a=32|_{:4} \Rightarrow a=8\ cm \ \ (latura \ p\breve atratului)[/tex]
5.
[tex]\it \mathcal{P}_{dreptunghi}=2(L+\ell)=30|_{:2} \Rightarrow L+\ell=15\ \ \ \ (*)[/tex]
Notăm latura pătratului cu a.
[tex]\it a=\dfrac{L}{3}=\dfrac{\ell}{2} =\dfrac{L+\ell}{3+2}\ \stackrel{(*)}{=}\ \dfrac{15}{5}=3\ cm\\ \\ \\ \mathcal{P}_{p\breve atrat}=4\cdot a=4\cdot3=12\ cm[/tex]
Suma perimetrelor celor șase pătrate este 6 · 12 = 72 cm
