a)

$P=2\cdot \left(20\text{cm}\cdot 40\text{cm}+20\text{cm}\cdot 30\text{cm}+30\text{cm}\cdot 40\text{cm}\right)=2\cdot \left(800{\text{cm}}^2+600{\text{cm}}^2+1200{\text{cm}}^2\right)=2\cdot 2600{\text{cm}}^2=5200{\text{cm}}^2$  

 

b)

$P=2\cdot \left(4\text{cm}\cdot 1\text{cm}+4\text{cm}\cdot 7\text{cm}+7\text{cm}\cdot 1\text{cm}\right)=2\cdot \left(4{\text{cm}}^2+28{\text{cm}}^2+7{\text{cm}}^2\right)=2\cdot 39{\text{cm}}^2=78{\text{cm}}^2$  

 

c)

$P=6\cdot 30\text{mm}\cdot 30\text{mm}=6\cdot 900{\text{mm}}^2=5400{\text{mm}}^2$  

 

d)

$P=2\cdot \left(5\text{m}\cdot 2\text{m}+5\text{m}\cdot 1\text{m}+1\text{m}\cdot 2\text{m}\right)=2\cdot \left(10{\text{m}}^2+1{\text{m}}^2+2{\text{m}}^2\right)=2\cdot 13{\text{m}}^2=26{\text{m}}^2$  

 

e)

Wymiary prostopadłościanu:

0,2m = 20cm

4,2dm = 42cm

21 cm 

$P=2\cdot \left(20\text{cm}\cdot 42\text{cm}+20\text{cm}\cdot 21\text{cm}+21\text{cm}\cdot 42\text{cm}\right)=2\cdot \left(840{\text{cm}}^2+420{\text{cm}}^2+882{\text{cm}}^2\right)=2\cdot 2142{\text{cm}}^2=4284{\text{cm}}^2$