a)

$P=2\cdot \left(2\text{cm}\cdot 3\text{cm}+2\text{cm}\cdot 5\text{cm}+3\text{cm}\cdot 5\text{cm}\right)=2\cdot \left(6{\text{cm}}^2+10{\text{cm}}^2+15{\text{cm}}^2\right)=2\cdot 31{\text{cm}}^2=62{\text{cm}}^2$  

 

b)

$P=6\cdot 4\text{cm}\cdot 4\text{cm}=6\cdot 16{\text{cm}}^2=96{\text{cm}}^2$  

 

c)

1,2 dm = 12 cm  

$P=2\cdot \left(12\text{cm}\cdot 12\text{cm}+12\text{cm}\cdot 36\text{cm}+12\text{cm}\cdot 36\text{cm}\right)=2\cdot \left(144{\text{cm}}^2+432{\text{cm}}^2+432{\text{cm}}^2\right)=2\cdot 1008{\text{cm}}^2=2016{\text{cm}}^2$