五年级上册数学《小数乘法》简便运算

五年级上册数学《小数乘法》简便运算1.乘法交换律、结合律2.5×8.7×0.4‌=2.5×0.4×8.7=(2.5×0.4)×8.7=1×8.7=‌8.7‌0.25×6.8×0.4‌=0.25×0.4×6.8=0.1×6.8=‌0.68‌2.5×1.75×8‌=2.5×8×1.75=20×1.75=‌35‌0.5×3.38×0.2‌=0.5×0.2×3.38=0.1×3.38=‌0.338‌0.4×68.9×0.25‌=0.4×0.25×68.9=0.1×68.9=‌6.89‌1.25×0.4×0.25×8‌=1.25×8×0.4×0.25=(1.25×8)×(0.4×0.25)=10×0.1=‌12.乘法分配律及逆应用‌（1.25-0.125）×8‌=1.25×8-0.125×8=10-1=‌9‌（20-0.4）×0.25‌=20×0.25-0.4×0.25=5-0.1=‌4.9‌‌3.97×0.92+3.97×0.08‌=3.97×(0.92+0.08)=3.97×1=‌3.97‌10.2×3.76-0.2×3.76‌=(10.2-0.2)×3.76=10×3.76=‌37.63.乘法分配律的拓展9.85×101‌=9.85×(100+1)=9.85×100+9.85×1=985+9.85=‌994.85‌37.65×99‌=37.65×(100-1)=37.65×100-37.65×1=3765-37.65=‌3727.35‌2.5×104‌=2.5×(100+4)=2.5×100+2.5×4=250+10=‌260‌9.8×1.01‌=9.8×(1+0.01)=9.8×1+9.8×0.01=9.8+0.098=‌9.8984.添加因数“1”6.32+6.32×99‌=6.32×1+6.32×99=6.32×(1+99)=6.32×100=‌632‌5.8×101-5.8‌=5.8×101-5.8×1=5.8×(101-1)=5.8×100=‌580‌4.81×99+4.81‌=4.81×99+4.81×1=4.81×(99+1)=4.81×100=‌481‌46.7×1001-46.7‌=46.7×1001-46.7×1=46.7×(1001-1)=46.7×1000=‌467005.拆分因数1.25×3.2‌=1.25×(8×0.4)=(1.25×8)×0.4=10×0.4=‌4‌4.8×0.25‌=(4×1.2)×0.25=4×(1.2×0.25)=4×0.3=‌1.2‌2.5×32×1.25‌=2.5×(8×4)×1.25=(2.5×4)×(8×1.25)=10×10=‌100‌12.5×0.64×2.5‌=12.5×(0.8×0.8)×2.5=(12.5×0.8)×(0.8×2.5)=10×2=‌206.移动小数点6.8×3.1+68×0.69‌=6.8×3.1+6.8×6.9=6.8×(3.1+6.9)=6.8×10=‌68‌0.54×30.8+3.08×4.6‌=5.4×3.08+3.08×4.6=3.08×（4.6+5.4）=3.08×10=30.8‌1.45×1.8+14.5×0.82‌=1.45×1.8+1.45×8.2=1.45×(1.8+8.2)=1.45×10=‌14.5‌1.5×2.8+72×0.15‌=1.5×2.8+7.2×1.5=1.5×(2.8+7.2)=1.5×10=‌15‌2.3×16+2.3×23+2.3‌=2.3×16+2.3×23+2.3×1=2.3×(16+23+1)=2.3×40=‌92‌314×0.043+3.14×7.2-3.14×1.5‌=3.14×4.3+3.14×7.2-3.14×1.5=3.14×(4.3+7.2-1.5)=3.14×10=‌31.4‌2.6×7.4+0.26×25+0.026×10‌=0.26×74+0.26×25+0.26×1=0.26×(74+25+1)=0.26×1