用你喜欢的方法计算. ×+1.25×3.375+4.2+8.25+5.8-(+)÷408+540÷18×2468÷[1÷(0.1-0.09)](+)×90-11.
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解:(1)×+1.25×3.3,
=8.375+4.125,
=12.5;
(2)75+4.2+8.25+5.8,
=75+8.25+(4.2+5.8),
=83.25+10,
=93.25;
(3)-(+)÷,
=-×,
=-,
=;
(4)408+540÷18×24,
=408+540÷18×24,
=408+720,
=1128;
(5)68÷[1÷(0.1-0.09)],
=68÷[1÷0.01],
=68÷100,
=0.68;
(6)(+)×90-11,
=×90+×90-11,
=6+5-11,
=0.
解析分析:(1)先算乘法,再算加法;(2)运用加法交换律与结合律简算;(3)先算括号内的,再算括号外的除法,最后算减法;(4)先算除法和乘法,再算加法;(5)先算小括号内的,再算中括号内的,最后算括号外的;(6)运用乘法分配律计算(+)×90,然后算减法.
点评:此题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算律简便计算.