计算下面各题,能简便的要用简便方法计算. ÷÷×6+×÷(-)÷-×(0.25+×)÷÷7+×(-)÷+.
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解:(1)÷÷,
=×27×,
=12;
(2)×6+,
=×(6+1),
=×7,
=5;
(3)×÷,
=××,
=;
(4)(-)÷,
=(-)×56,
=×56-×56,
=42-40,
=2;
(5)-×,
=(1-)×,
=×,
=;
(6)(0.25+×)÷,
=(+)×,
=1×,
=;
(7)÷7+×,
=×+×,
=×(+),
=×1,
=;
(8)(-)÷+,
=×6+,
=+,
=1.
解析分析:(1)(3)把除法改为乘法,约分计算;
(2)(5)运用乘法分配律简算;
(4)先算括号内的,再算括号外的;
(6)先算括号内的乘法,再算括号内的加法,最后算括号外的;
(7)把除法改为乘法,运用乘法分配律简算;
(8)先算括号内的,再算括号外的除法,最后算加法.
点评:此题考查了四则混合运算,注意运算顺序,运用运算定律灵活简算.