五年级上册数学《小数乘除法》简便运算8大常考题型,吃透计算不丢分~

五年级上册数学小数乘除法简便运算

一、乘法交换律

0.25×8.5×4

=0.25×4×8.5

=1×8.5

=8.5

12.5×0.96×0.8

=12.5×0.8×0.96

=10×0.96

=9.6

二、乘法结合律

4.36×12.5×8

=4.36×(12.5×8)

=4.36×100

=436

0.95×0.25×4

=0.95×(0.25×4)

=0.95×1

=0.95

三、拆数+乘法结合律

0.125×8.8

=0.125×8×1.1

=1×1.1

=1.1

0.25×0.28

=0.25×4×0.07

=1×0.07

=0.07

四、乘法分配律

(1.25-0.125)×8

=1.25×8-0.125×8

=10-1

=9(正用)

(125+2.5)×0.8

=125×0.8+2.5×0.8

=1+1

=2(正用)

五、拆分，再按乘法分配律

0.8×100.1

=0.8×(100+0.1)

=0.8×100+0.8×0.1

=80+0.08

=80.08

4.6×0.9

=4.6×(1-0.1)

=4.6×1-4.6×0.1

=4.6-0.46

=4.14

3.65×10.1

=3.65×(10+0.1)

=3.65×10+3.65×0.1

=36.5+0.365

=36.865

0.85×199

=0.85×(200-1)

=0.85×200-0.85×1

=170-0.85

=169.15

六、添加因数“1”

56.5×99+56.5

=56.5×99+56.5×1

=56.5×(99+1)

=56.5×100

=5650

5.4×11-5.4

=5.4×11-5.4×1

=5.4×(11-1)

=54

9.7×99+9.7

=9.7×99+9.7×1

=9.7×(99+1)

=9.7×100

=970

1.87×9.9+0.187

=1.87×9.9+1.87×0.1

=1.87×(9.9+0.1)

=18.7

七、更改因数的小数点位置

6.66×3.3+0.666×67

=6.66×3.3+6.66×6.7

=6.66×(3.3+6.1)

=6.66×10

=66.6

101×0.87-0.91×87

=1.01×87-0.91×87

=87×(1.01-0.91)

=87×0.1

=8.7

八、除法的性质

正用:a÷b÷c=a÷(b×c)

320÷1.25÷8

=320÷(1.25×8)

=320÷10

=32

9.6÷0.8÷4

=9.6÷(0.8×4)

=9.6÷3.2

=3

逆用:a÷(b×c)=a÷b÷c

3.9÷(1.3×5)

=3.9÷1.3÷5

=3÷5

=0.6

15÷(0.15×0.4)

=15÷0.15÷0.4

=100÷0.4

=250

九、综合练习题

32×1.25

=4×(8×1.25)

=4×10

=40

0.125×96

=0.125×8×12

=1×12

=12

2.34×99＋2.34

＝2.34×（99＋1）

＝2.34×100

＝234

2.5×16

＝（2.5×4）×4

＝10×4

＝40

1.25×2.4

＝1.25×8×0.3

＝10×0.3

＝3

0.45×99

=0.45×(100-1)

=0.45×100-0.45×1

=44.55

45×1.58+5.5×15.8

=45×1.58+55×1.58

=1.58×(45+55)

=158

132×101

＝132×（100＋1）

＝132×100＋132

＝13332

6.33×101﹣6.33

＝6.33×（101﹣1）

＝6.33×100

＝633

1.56×1.7＋0.44×1.7

＝1.7×(1.56＋0.44)

＝1.7×2

＝3.4

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