a) P(ABC) = AB + AC + BC = 3 × 9,7 = 29,1 cm
b) AB = 2AC = 16 cm => AC = 16 : 2 = 8 cm
BC = 10,6 cm
P(ABC) = 16 + 8 + 10,6 = 34,6 cm
c) AB = 0,8 × (AC + BC) = 12 cm
AC + BC = 12 : 0,8 = 120 : 8 = 15 cm
P(ABC) = 12 + 15 = 27 cm
d) AB + AC = 15 cm
AB + BC = 16 cm
AC + BC = 17 cm
AB + AC + AB + BC + AC + BC = 15 + 16 + 17
2 × (AB + AC + BC) = 48
AB + AC + BC = P(ABC) = 48 : 2 = 24 cm