五年级上册数学《小数乘法简便运算》7类

五年级上册数学《小数乘法简便运算》7类一、乘法交换律a×b×c=b×a×c0.25×8.5×4

=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

0.5×0.34×0.6=0.5×0.6×0.34=0.3×0.34=0.102二、乘法结合律a×b×c=a×(b×c)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

0.75×50×0.4=0.75×(50×0.4)=0.75×20=15三、乘法分配律(a+b)×c=a×c+b×c或【(a-b)×c=a×c-b×c】(1.25-0.125)×8=1.25×8-0.125×8=10-1

=9

(125+2.5)×0.8

=125×0.8+2.5×0.8=1+1

=2

3.72×3.5+6.28×3.5=3.5×(3.5+6.28)=3.5×10

=35四、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

0.125×3.2×2.5

=(0.125×8)×(0.4×2.5)

=1×1=1五年级上册数学《小数乘法简便运算》7类五、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=0.8×(100+0.1)

=0.8×100+0.8×0.1

=80+0.08=80.08

3.65×10.1

=3.65×(10+0.1)

=3.65×10+3.65×0.1

=36.5+0.365

=36.865

4.6×0.9

=4.6×(1-0.1)=4.6×1-4.6×0.1=4.6-0.46

=4.14

0.79×99=0.79×(100-1)

=0.79×100-0.79×1=79-0.79

=78.21六、添加因数“1”56.5×99+56.5

=56.5×99+56.5×1

=56.5×(99+1)

=56.5×100=5650

9.7×99+9.7

=9.7×99+9.7×1

=9.7×(99+1)

=9.7×100

=970

4.2×99+4.2=4.2×99+4.2×1=4.2×(99+1)

=4.2×100

=4205.4×11-5.4

=5.4×11-5.4×1

=5.4×(11-1)

=54

1.87×9.9+0.187

=1.87×9.9+1.87×0.1=1.87×

(9.9+0.1)

=18.7

12.7×9.9+1.27=1.27×99+1.27×1=1.27×(99+1)

=127五年级上册数学《小数乘法简便运算》7类七、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+6.7)

=6.66×10=66.6

0.54×30.8+3.08×4.6=5.4×3.08+3.08×4.6=3.08×（5.4+4.6）=3.08×10=30.84.8×7.8+78×0.52

=4.8×7.8+7.8×5.2=7.8×(4.8+5.2)

=7.8×10

=783.14×0.68+31.4×0.032

=3.14×0.68+3.14×0.32

=3.14×(0.68+0.32)

=3.14×1

=314

101×0.87-0.91×87=1.01×87-0.91×87=87×(1.01-0.91)

=87×0.1=8.

72.3×16+2.3×23+0.23×10

=2.3×16+2.3×23+2.3×1=2.3×

(16+23+1)

=2.3×40

=92314×0.043+3.14×7.2-31.4×0.15=3.14×4.3+3.14×7.2-3.14×1.5=3.14×(4.3