Convert 20 m² in cm²

$20 {\mathrm{m}}^2 =20 {\left(\mathrm{m}\right)}^2$  (We know that 1 m= 100 cm)

$={20 (100 \mathrm{cm})}^2=20\times 100 \mathrm{cm} \times 100 \mathrm{cm}$

$=200000 {\mathrm{cm}}^2$

Therefore, $20 {\mathrm{m}}^2 = 200000 {\mathrm{cm}}^2$.