五上数学【小数乘法】简便计算专练

五上数学【小数乘法】简便计算专练一、乘法交换律(1)2.5×9×4=2.5×4×9=10×9=90(2)1.5×7×6=1.5×6×7=9×7=63(3)0.8×1.4×12.5=0.8×12.5×1.4=10×1.4=14(4)0.5×0.34×6=0.5×6×0.34=3×0.34=1.2(5)0.25×0.46×40=0.25×40×0.46=10×0.46=4.6(6)0.8×0.46×0.5=0.8×0.5×0.46=0.4×0.46=0.184二、乘法结合律(1)4.31×1.25×0.8=4.31×1=4.31(2)0.79×5×2=0.79×10=7.9(3)0.16×2.5×400=0.16×1000=160(4)12.56×0.4×5=12.56×2=25.12(5)4.7×8×0.5=4.7×4=18.8(6)3.36×0.05×6=3.36×0.3=1.008三、乘法交换律与结合律(1)2.5×50×0.6×0.4=2.5×0.4×50×0.6=1×30=30(2)0.8×0.04×12.5×250=0.8×12.5×0.04×250=10×10=100(3)0.6×0.125×0.8×50=0.6×50×0.125×0.8=30×0.1=3(4)1.5×0.4×2.5×0.2=1.5×0.2×0.4×2.5=0.3×1=0.3四、乘法分配律(加减法)(1)0.64×28+72×0.64=0.64×(28+72)=0.64×100=64(2)3.12×0.49-0.12×0.49=0.49×(3.12-0.12)=0.49×3=1.47(3)6.6×5.8+3.4×5.8=5.8×(6.6+3.4)=5.8×10=58(4)26.45×0.4-0.4×1.45=0.4×(26.45-1.45)=0.4×25=10(5)1.3×2.5+0.7×2.5=2.5×(1.3+0.7)=2.5×2=5(6)3.62×0.08-2.37×0.08=0.08×(3.62-2.37)=0.08×1.25=0.1五、乘法分配律(拆分法)(1)0.65×101=0.65×(100+1)=0.65×100+0.65×1=65+0.65=65.65(2)5.1×99=5.1×(100-1)=5.1×100-5.1×1=510-5.1=504.9(3)0.79×102=0.79×(100+2)=0.79×100+0.79×2=79+1.58=80.58(4)1.36×99=1.36×(100-1)=1.36×100-1.36×1=136-1.36=134.64(5)1.25×0.88=1.25×(0.8+0.08)=1.25×0.8+1.25×0.08=1+0.1=1.1(6)0.25×4.4=0.25×(4+0.4)=0.25×4+0.25×0.4=1+0.1=1.1(7)1.25×4.8=1.25×(0.8+4)=1.25×0.8+1.25×4=1+5=6(8)2.5×36=2.5×(40-4)=2.5×40-2.5×4=100-10=90六、混合练习(1)0.25×6.14×0.4=0.25×0.4×6.14=0.1×6.14=0.614(2)44×0.33+56×0.33=0.33×(44+56)=0.33×100=33(3)7.36×101=7.36×(100+1)=7.36×100+7.36×1=736+7.36=743.36(4)2.5×204=2.5×(200+4)=2.5×200+2.5×4=500+10=510(5)3.2×1.25=0.4×8×1.25=0.4×10=4(6)9.44×99+9.44=9.44×(99+1)=9.44×100=944(7)(1.25-0.5)×0.8=1.25×0.8-0.5×0.8=1-0.4=0.6(8)58.97×101-58.97=58.97×(101-1)=58.97×100=5897(9)