a)

Wiemy, że:

$1\text{dm}=10\mathrm{cm}$

zatem:

$1{\text{dm}}^2=1\text{dm}\cdot 1\text{dm}=10\mathrm{cm}\cdot 10\mathrm{cm}=100{\mathrm{cm}}^2$

Wtedy:

$5{\text{dm}}^2=5\cdot 1{\text{dm}}^2=5\cdot 100{\mathrm{cm}}^2=\underline{500{\mathrm{cm}}^2}$

---

b)

Wiemy, że:

$1\text{ha}=100\text{a}$

Wtedy:

$0,4\text{ha}=0,4\cdot 1\text{ha}=0,4\cdot 100\text{a}=\underline{40\text{a}}$

---

c)

Wiemy, że:

$1\text{m}=100\mathrm{cm}=1000\mathrm{mm}$

Zatem:

$1{\text{m}}^2=1\text{m}\cdot 1\text{m}=1000\mathrm{mm}\cdot 1000\mathrm{mm}=1000000{\mathrm{mm}}^2$

Wtedy:

$11{\text{m}}^2=11\cdot 1{\text{m}}^2=11\cdot 1000000{\mathrm{mm}}^2=\underline{11000000{\mathrm{mm}}^2}$

---

d)

Wiemy, że:

$1\text{a}=100{\text{m}}^2=10000{\text{dm}}^2$

Wtedy:

$6\text{a}=6\cdot 1\text{a}=6\cdot 10000{\text{dm}}^2=\underline{60000{\text{dm}}^2}$

---

e)

Wiemy, że:

$1\mathrm{mm}=0,1\mathrm{cm}$

Zatem:

$1{\mathrm{mm}}^2=1\mathrm{mm}\cdot 1\mathrm{mm}=0,1\mathrm{cm}\cdot 0,1\mathrm{cm}=0,01{\mathrm{cm}}^2$

Wtedy:

$75{\mathrm{mm}}^2=75\cdot 1{\mathrm{mm}}^2=75\cdot 0,01{\mathrm{cm}}^2=\underline{0,75{\mathrm{cm}}^2}$

---

f)

Wiemy, że:

$1\text{a}=10000{\text{dm}}^2$

Zatem:

$1{\text{dm}}^2=0,0001\text{a}$

Wtedy:

$227{\text{dm}}^2=227\cdot 1{\text{dm}}^2=227\cdot 0,0001\text{a}=\underline{0,0227\text{a}}$

---

g)

Wiemy, że:

$1\text{dm}=0,1\text{m}=0,0001\mathrm{km}$

Zatem:

$1{\text{dm}}^2=1\text{dm}\cdot 1\text{dm}=0,0001\mathrm{km}\cdot 0,0001\mathrm{km}=0,00000001{\mathrm{km}}^2$

Wtedy:

$620{\text{dm}}^2=620\cdot 1{\text{dm}}^2=620\cdot 0,00000001{\mathrm{km}}^2=\underline{0,0000062{\mathrm{km}}^2}$

---

h)

Wiemy, że:

$1\text{ha}=100\text{a}=10000{\text{m}}^2$

Zatem:

$1{\text{m}}^2=0,0001\text{ha}$

Wtedy:

$800{\text{m}}^2=800\cdot 1{\text{m}}^2=800\cdot 0,0001\text{ha}=\underline{0,08\text{ha}}$