12.5×0.5×4×0.8 運(yùn)用
 
律和
 
律可以使計(jì)算簡便，得數(shù)是
 
．
分析：12.5×0.5×4×0.8=12.5×4×0.5×0.8=（12.5×4）×（0.5×0.8）=20；運(yùn)用了乘法交換律和乘法結(jié)合律，由此解答即可．
解答：解：12.5×0.5×4×0.8 
=12.5×4×0.5×0.8
=（12.5×4）×（0.5×0.8）
=50×0.4
=20；
運(yùn)用了乘法交換律和乘法結(jié)合律，得數(shù)是20；
故答案為：乘法交換，乘法結(jié)合，20．
點(diǎn)評(píng)：在利用運(yùn)算定律簡算時(shí)，要細(xì)心分析題目數(shù)據(jù)及運(yùn)算符號(hào)，選擇合適的運(yùn)算定律計(jì)算．
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