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整数乘法运算定律推广到小数

整数乘法运算定律推广到小数. 乘法交换律 : 两个数相乘，交换因数的位置，它们的积不变 。 axb=bxa 乘法结合律 : 三个数相乘，先把前两个数相乘，再同第三个数相乘，或者先把后两个数相乘，再同第一个数相乘，它们的积不变。（ axb)xc=ax(bxc) 乘法分配律 : 两个数的和同一个数相乘，可以把两个加数分别同这个数相乘，再把两个积相加，结果不变。 ax(b+c)=axc+bxc. 观察下面每组的两个算式，它们有什么关系？. 0.7x1.2 ○1.2x0.7 (0.8x0.5)x0.4 ○ 0.8x(0.5x0.4)

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整数乘法运算定律推广到小数

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  1. 整数乘法运算定律推广到小数

  2. 乘法交换律: 两个数相乘，交换因数的位置，它们的积不变。axb=bxa 乘法结合律: 三个数相乘，先把前两个数相乘，再同第三个数相乘，或者先把后两个数相乘，再同第一个数相乘，它们的积不变。（axb)xc=ax(bxc) 乘法分配律: 两个数的和同一个数相乘，可以把两个加数分别同这个数相乘，再把两个积相加，结果不变。ax(b+c)=axc+bxc

  3. 观察下面每组的两个算式，它们有什么关系？ 0.7x1.2 ○1.2x0.7 (0.8x0.5)x0.4 ○ 0.8x(0.5x0.4) (2.4+3.6)x0.5 ○ 2.4x0.5+3.6x0.5

  4. 0.7x1.2 =1.2x0.7 (0.8x0.5)x0.4 = 0.8x(0.5x0.4) (2.4+3.6)x0.5 = 2.4x0.5+3.6x0.5

  5. 下面各题怎样简便就怎样算？想一想依据是什么？下面各题怎样简便就怎样算？想一想依据是什么？ 0.25x4.78x4 =0.25x4x4.78 乘法交换律 = 1x4.78 = 4.78 0.65x201 =0.65x(200+1) 乘法分配律 =0.65x200+0.65x1 =130+0.65 =130.65

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