五上数学.小数乘除法简便计算

五上数学.小数乘除法简便计算分类练习题第一种：乘法交换律2.5×9×4=2.5×4×9=10×9=901.5×7×6=1.5×6×7=9×7=630.8×1.4×12.5=0.8×12.5×1.4=10×1.4=140.25×0.46×40=0.25×40×0.46=10×0.46=4.60.5×0.34×6=0.5×6×0.34=3×0.34=1.020.25×6.14×0.4=0.25×0.4×6.14=0.1×6.14=0.614第二种：乘法结合律4.31×1.25×0.8=4.31×(1.25×0.8)=4.31×1=4.310.79×5×2=0.79×(5×2)=0.79×10=7.90.16×2.5×400=0.16×(2.5×400)=0.16×1000=1602.5×50×0.6×0.4=(2.5×0.4)×(50×0.6)=1×30=3012.5×32×2.5=12.5×(8×4)×2.5=(12.5×8)×(4×2.5)=100×10=1000第三种：乘法分配律（逆合型）0.64×28+72×0.64=0.64×(28+72)=0.64×100=643.12×0.49-0.12×0.49=0.49×(3.12-0.12)=0.49×3=1.47第四种：乘法分配率（顺展型）0.8×(12.5-1.25)=0.8×12.5-0.8×1.25=10-1=9(2+0.4+0.04)×5=2×5+0.4×5+0.04×5=10+2+0.2=12.2拓展：(1.25+2.5)×8×4=1.25×8×4+2.5×4×8=10×4+10×8=40+80=1200.4×(0.25+12.5)×8=0.4×0.25×8+0.4×12.5×8=0.1×8+5×8=0.8+40=40.8第五种：拆分型（拆加、拆减、拆乘）0.65×10.1=0.65×(10+0.1)=0.65×10+0.65×0.1=6.5+0.065=6.5650.79×102=0.79×(100+2)=0.79×100+0.79×2=79+1.58=80.585.1×99=5.1×(100-1)=5.1×100-5.1×1=510-5.1=504.91.36×99=1.36×(100-1)=1.36×100-1.36×1=136-1.36=134.641.25×0.88=1.25×(8×0.11)=1.25×8×0.11=10×0.11=1.112.5×0.32×2.5=12.5×(0.08×4)×2.5=(12.5×0.08)×(4×2.5)=1×10=10第六种：添加因数“1”1.8×99+1.8=1.8×99+1.8×1=1.8×(99+1)=1.8×100=1803.8×9.9+0.38=3.8×9.9+3.8×0.1=3.8×(9.9+0.1)=3.8×10=380.67×10.1-6.7=0.67×10.1-0.67×10=0.67×(10.1-10)=0.67×0.1=0.0673.5×101-3.5=3.5×101-3.5×1=3.5×(101-1)=3.5×100=350第七种：更改因数小数点的位置（积不变性质）6.66×3.3+0.666×67=6.66×3.3+6.66×6.7=6.66×(3.3+6.7)=6.66×10=66.64.8×7.8+78×0.52=4.8×7.8+7.8×5.2=7.8×(4.8+5.2)=7.8×10=782.3×16+2.3×32+2.3=2.3×16+2.3×32+2.3×1=2.3×(16+32+1)=2.3×49=112.70.54×30.8+3.08×4.6=5.4×3.08+3.08×4.6=3.08×(5.4+4.6)=3.08×10=30.8第八种：除法的性质a÷b÷c=a÷(b×c)7÷0.125÷8=7÷(0.125×8)=7÷1=780÷0.5÷0.4=80÷(0.5×0.4)=80÷0.2=400300÷2.5÷4=300÷(2.5×4)=300÷10=3012.5÷(12.5×4)=12.5÷12.5÷4=1÷4=0.257.6÷(0.76×2)=7.6÷0.76÷2=10÷2=53.14÷(0.0314×8)=3.14÷0.0314÷8=100÷8=12.5第九种：移项（带着符号搬家）1.25÷25×0.8=1.25×0.8÷25=1÷25=0.04102×7.3÷5.1=102÷5.1×7.3=20×7.3=1463.6×0.5÷3.6×0.5=3.6÷3.6×0.5×0.5=1×0.25=0.2558÷25÷0.58=58÷0.58÷25=100÷25=4第十种：拆括号（括号前是乘号，去括号不变号）1.25×(8÷0.5)=1.25×8÷0.5=10÷0.5=200.25×(4×1.2)=0.25×4×1.2=1×1.2=1.27.2×(4.3÷7.2)=7.2÷7.2×4.3=1×4.3=4.31.25×(213×0.8)=1.25×0.8×213=1×213=2135.4×(0.75÷5.4)=5.4÷5.4×0.75=1×0.75=0.756.6×(0.8÷3.3)=6.6÷3.3×0.8=2×0.8=1.6第十一种：拆括号（括号前是除号，去括号要变号）10.8÷(3.6÷0.75)=10.8÷3.6×0.75=3×0.75=2.253.6÷(12.5×4)=3.6÷12.5÷4=3.6÷(12.5×4)=3.6÷50=0.0723.9÷(1.3÷0.3)=3.9÷1.3×0.3=3×0.3=0.917.8÷(1.78×0.4)=17.8÷1.78÷0.4=10÷0.4=25第十二种：同扩同缩商不变A÷B=(A×C)÷(B÷C)13.6÷0.5=(13.6×2)÷(0