五年级上册数学小数乘法简便运算专项练习

五年级上册数学小数乘法简便运算专项练习一、乘法交换律0.25×8.5×4 12.5×0.96×0.8 0.5×0.34×0.6=0.25×4×8.5 =12.5×0.8×0.96 =0.5×0.6×0.34=1×8.5 =10×0.96 =0.3×0.34=8.5 =9.6 =0.102二、乘法结合律4.36×12.5×8 0.95×0.25×4 0.75×50×0.4=4.36×(12.5×8) =0.95×(0.25×4) =0.75×(50×0.4)=4.36×100 =0.95×1 =0.75×20=436 =0.95 =15三、拆数+乘法结合律0.125×8.80.25×0.28 0.125×3.2×2.5=0.125×8×1.1=0.25×4×0.07 =(0.125×8)×(0.4×2.5)=1×1.1=1×0.07 =1×1=1.1=0.07 =1四、乘法分配律(1.25-0.125)×8 (125+2.5)×0.8 3.72×3.5+6.28×3.5=1.25×8-0.125×8=125×0.8+2.5×0.8 =3.5×(3.5+6.28)=10-1=1+1 =3.5×10=9(正用) =2(正用) =35(逆用)五、把其中一个因数分成两个数的和或差，再按乘法分配律0.8×100.1 3.65×10.10.32×403=0.8×(100+0.1) =3.65×(10+0.1)=0.32×(400+3)=0.8×100+0.8×0.1 =3.65×10+3.65×0.1=0.32×400+0.32×3=80+0.08 =36.5+0.365=128+0.96=80.08 =36.865=128.964.6×0.9 0.85×199 0.79×99=4.6×(1-0.1) =0.85×(200-1) =0.79×(100-1)=4.6×1-4.6×0.1 =0.85×200-0.85×1 =0.79×100-0.79×1=4.6-0.46 =170-0.85 =79-0.79=4.14 =169.15 =78.21六、添加因数“1”56.5×99+56.5 9.7×99+9.7 4.2×99+4.2=56.5×99+56.5×1 =9.7×99+9.7×1 =4.2×99+4.2×1=56.5×(99+1) =9.7×(99+1) =4.2×(99+1)=56.5×100 =9.7×100=4.2×100=5650 =970 =4205.4×11-5.4 1.87×9.9+0.187 12.7×9.9+1.27=5.4×11-5.4×1 =1.87×9.9+1.87×0.1 =1.27×99+1.27×1=1.87×(9.9+0.1) =18.7 =1.27×(99+1)=5.4×(11-1) =127=54七、更改因数的小数点位置6.66×3.3+0.666×67 46×57+23×86 4.8×7.8+78×0.52=6.66×3.3+6.66×6.7 =46×57+46×43 =4.8×7.8+7.8×5.2=6.66×(3.3+6.1) =46×(57+43) =7.8×(4.8+5.2)=6.66×10 =46×100 =7.8×10 =66.6 =4600 =783.14×0.68+31.4×0.032 101×0.87-0.91×87=3.14×0.68+3.14×0.32 =1.01×87-0.91×87=3.14×(0.68+0.32) =87×(1.01-0.91)=3.14×1 =87×0.1=314 =8.72.3×16+2.3×23+2.3 314×0.043+3.14×7.2-31.4×0.15=2.3×16+2.3×23+2.3×1=3.14×4.3+3.14×7.2-3.14×1.5=2.3×(16+23+1)=3.14×(4.3+7.2-1.5)=2.3×40=3.14×10=92 =31.4八、除法的性质正用:a÷b÷c=a÷(b×c)320÷1.25÷8 3.52÷2.5÷0.4 9.6÷0.8÷4=320÷(1.25×8) =3.52÷(2.5×0.4) =9.6÷(0.8×4)=320÷10 =3.52÷1 =9.6÷3.2=32 =3.52 =3逆用:a÷(b×c)=a÷b÷c3.9÷(1.3×5) 15÷(0.15×0.4) 75.3÷(7.53×20)=3.9÷1.3÷5 =15÷0.15÷0.4 =75.3÷7.53÷20=3÷5 =100÷0.4 =10÷20=0.6 =250 =0.5九、综合练习题5×1.03×0.2 32×1.25 0.45×99=5×0.2×1.03 =4×(8×1.25) =0.45×(100-1)=1×1.03 =4×10 =0.45×100-0.45×1=1.03 =40 =44.550.125×96 45×1.58+5.5×15.89.99×2.22+3.33×3.34=0.125×8×12 45×1.58+55×1.58=3.33×6.66+3.33×3.34=1×12=1.58×(45+55)=3.33×(6.66+3.34)=12=158=33.3