口算下面各题: 0.1×8.1 = 0.3×0.7 = 720-580= 0.2×0.34= 0.2+0.85= 1.5×6= 3.04×1000= 0.4×0.25= 8.2+1.8= 1.4-0.9= 480÷16= 2-0.54=