1)
[tex]1 \ km^2=(1000 \ m)^2=1 \ 000 \ 000 \ m^2\\\\0,5 \ km^2=0,5\cdot1 \ 000 \ 000 \ m^2=\boxed{500 \ 000 \ m^2}[/tex]
2)
[tex]2 \ km^2=2\cdot1 \ 000 \ 000 \ m^2=\boxed{2 \ 000 \ 000 \ m^2}\\[/tex]
3)
[tex]1 \ m^2=(100 \ cm)^2=10 \ 000 \ cm^2\\\\1 \ cm^2=0,0001 \ m^2\\\\12 \ 500 \ cm^2=12 \ 500\cdot0,0001 \ m^2=\boxed{1,25 \ m^2}[/tex]
4)
[tex]1 \ m^2=(10 \ dm)^2=100 \ dm^2\\\\1 \ dm^2=0,01 \ m^2\\\\2500 \ dm^2=2500\cdot0,01 \ m^2=\boxed{25 \ m^2}[/tex]