a) \(7km^2= 7 \;000\; 000m^2\)
\(4ha = 40 \;000m^2\)
\(8,5 ha =8 \dfrac{5}{10}ha = 8 \dfrac{5000}{10000}ha \)\(= 8ha\; 5000 m^2= 8 500 0 m^2\)
b) \(\displaystyle 30 dm^2={30\over 100}m^2=0,30m^2 =0,3 m^2\)
\(300dm^2= 3m^2\)
\(515dm^2 = 500dm^2 + 15dm^2 \)\( = 5{m^2}\; 15d{m^2} = 5\dfrac{{15}}{{100}}{m^2} = 5,15{m^2}\).