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简介:
一、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)
二、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 0.32×403
=0.8×(100+0.1) =0.32×(400+3)
=0.8×100+0.8×0.1 =0.32×400+0.32×3
=80+0.08 =128+0.96
=80.08 =128.96
三、更改因数的小数点位置
6.66×3.3+0.666×67 46×57+23×86
=6.66×3.3+6.66×6.7 =46×57+46×43
=6.66×(3.3+6.1) =46×(57+43)
=6.66×10 =46×100
=66.6 =4600