Explicație pas cu pas:
ΔABC ~ ΔPQR
[tex]\frac{AB}{PQ} = \frac{BC}{QR} = \frac{AC}{PR} \iff \frac{7}{PQ} = \frac{BC}{36} = \frac{9}{21} = \frac{3}{7} \\ [/tex]
[tex]PQ = \frac{7 \cdot 7}{3} = \frac{49}{3} \: cm \\ BC = \frac{36 \cdot 3}{7} = \frac{108}{7} \: cm[/tex]
→
[tex]P(\triangle ABC) = AB + AC + BC = 7 + 9 + \frac{108}{7} = \frac{220}{7} \: cm \\ [/tex]
[tex]P(\triangle PQR) = PQ + PR + QR = \frac{49}{3} + 21 + 36 = \frac{220}{3} \\ [/tex]
