(1)∵1m=10dm,∴1.2m=1.2×10dm=12dm;
∵1m=103mm,∴1.2m=1.2×103mm=1200mm;
∵1m=109nm,∴1.2m=1.2×109nm;
(2)∵1dm=10-4km,∴0.6×102dm=0.6×102×10-4km=6×10-3km;
∵1dm=105μm,∴0.6×102dm=0.6×102×105μm=6×106μm;
(3)∵1km/h=
m/s,∴72km/h=72×1 3.6
m/s=20m/s;1 3.6
1h=60min=3600s.
故答案为:(1)12;1200;1.2×109;(2)6×10-3;6×106;(3)20;60;3600.