25 cm: 12 km=______ :______ =______ 450 G: 12 kg=______ :______ =______ 5:00: 1:40=______ :______ =______ .

25 cm: 12 km=______ :______ =______ 450 G: 12 kg=______ :______ =______ 5:00: 1:40=______ :______ =______ .

(1) 25 cm: 12 km = 25 cm: 50000 cm = 1:2000 = 0.0005; (2) 450 G: 12 kg = 450 G: 500 g = 9:10 = 0.9; (3) 5:00: 1:40 = 300: 100 = 3:1 = 3