计算下面各题,怎样简便就怎样算.
1.65÷5+1.29×0.2+×20%????????????????
(+)×3+
×[-(-)]
24×(-)÷.
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解:(1)1.65÷5+1.29×0.2+×20%,
=1.65×0.2+1.29×0.2+0.06×0.2,
=(1.65+1.29+0.06)×0.2,
=3×0.2,
=0.6;
?
(2)(+)×3+,
=++,
=1+,
=;
(3)×[-(-)],
=×[+-],
=×[1-],
=×,
=;
(4)24×(-)÷,
=[24×-24×],
=[9-4],
=5,
=25.
解析分析:(1)把题中的分数化为小数,再把1.65÷5化为1.65×0.2,运用乘法分配律解答,(2)先运用乘法分配律,再运用加法交换律解答,(3)运用减法的性质解答,(4)运用乘法分配律解答.
点评:本题主要考查了学生运用四则运算简便算法解决问题的能力.