五上数学小数乘除法简便计算归类
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简介
一、乘法交换律a×b=b×a 2.5×4.8×0.4 =2.5×0.4×4.8 =1×4.8 =4.8 0.125×7.2×8 =0.125×8×7.2 =1×7.2 =7.2 0.5×3.69×2 =0.5×2×3.69 =1×3.69 =3.69 二、乘法交换律、结合律：a×b=b×a(a×b)×c=a×(b×c) 1.25×0.88×0.8 =0.88×(1.25×0.8) =0.88×1 =0.88 0.25×3.2×1.25 =(0.25×4)×(0.8×1.25) =1×1 =1 2.5×0.44×4 =0.44×(2.5×4) =0.44×10 =4.4 三、乘法分配律(顺展型)：(a±b)×c=a×c±b×c (4+0.8)×25 =4×25+0.8×25 =10+20 =30 8.5×(10-2)
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