题目内容
计算(要写过程)
(1);
(2)
(3)78.6-0.786×25+75%×21.4.
解:(1)×-×,
=×16×-×2×,
=(×16-×2)×,
=()×,
=×,
=;
(2)6÷[35×()]×4.8,
=6÷[35×+35×]×4.8,
=6÷[14+10]×4.8,
=6÷24×4.8,
=×4.8,
=1.2;
(3)78.6-0.786×25+75%×21.4,
=0.786×100-0.786×25+0.75×21.4,
=0.786×(100-25)+0.75×21.4),
=0.786×75+0.214×75,
=(0.786+0.214)×75,
=1×75,
=75.
分析:(1)×-×转化成×16×-×2×然后根据乘法的分配律计算;
(2)35×()用乘法的分配律计算;
(3)78.6-0.786×25+75%×21.4转化成0.786×100-0.786×25+0.75×21.4然后根据乘法的分配律计算.
点评:此题主要训练学生进行四则运算时,灵活地运用简便计算.
=×16×-×2×,
=(×16-×2)×,
=()×,
=×,
=;
(2)6÷[35×()]×4.8,
=6÷[35×+35×]×4.8,
=6÷[14+10]×4.8,
=6÷24×4.8,
=×4.8,
=1.2;
(3)78.6-0.786×25+75%×21.4,
=0.786×100-0.786×25+0.75×21.4,
=0.786×(100-25)+0.75×21.4),
=0.786×75+0.214×75,
=(0.786+0.214)×75,
=1×75,
=75.
分析:(1)×-×转化成×16×-×2×然后根据乘法的分配律计算;
(2)35×()用乘法的分配律计算;
(3)78.6-0.786×25+75%×21.4转化成0.786×100-0.786×25+0.75×21.4然后根据乘法的分配律计算.
点评:此题主要训练学生进行四则运算时,灵活地运用简便计算.
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