单位换算:3m=______mm=______um 300mm=________m=_______km 4.6×10的六
单位换算:3m=______mm=______um 300mm=________m=_______km 4.6×10的六次方nm=______mm=______m
20km=_________________=_______m
5.6×10的6次方m=____________________________=______nm
300cm=___________________=________um