文档文本内容
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
0.125×8.8 0.25×0.28 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 3.65×10.1 0.32×403
=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 =128.96
4.6×0.9 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 =78
3.14×0.68+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. 7
2.3×16+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÷c
3.9÷ (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)
=1×1.0 3 =4×10 =0.45×100-
0.45×1
=1.03 =40 =44.55
0.125×96 45×1.58+5.5×15.8
9.99×2.22+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
