a) 5cm2 = 500 mm2
$1m^{2}$= 10000 $cm^{2}$
$12km^{2}$= 1200 $hm^{2}$
$5m^{2}$= 50000 $cm^{2}$
$1hm^{2}$= 10000 $m^{2}$
12m2 9dm2= 1209 $dm^{2}$
$37dam^{2}24m^{2}$= 3724 $m^{2}$
b)
$800mm^{2}$= 8$cm^{2}$
3400dm2 = 34 m2
12 000hm2 = 120 km2
90 000m2 = 9 hm2
150cm2 =1 dm250cm2
2010m2 = 20 dam210 m2