脱式计算. (1)8-2×2÷1(2)30.8-22.2×0.5÷0.37(3)7.8-(-2.75)×(4)[10+(1.2-)÷0.11]×.
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解:(1)8-2×2÷1,
=8-÷1,
=8-,
=4.7;
(2)30.8-22.2×0.5÷0.37,
=30.8-11.1÷0.37,
=30.8-30,
=0.8;
(3)7.8-(-2.75)×,
=7.8-1×,
=7.8-,
=6.55;
(4)[10+(1.2-)÷0.11]×,
=[10+0.55÷0.11]×,
=[10+5]×,
=15×,
=6.
解析分析:(1)先算乘法,再算除法,最后算减法,
(2)先算乘法,再算除法,最后算减法,
(3)先算小括号里的减法,再算括号外的乘法,最后算减法,
(4)先算小括号里的减法,再算中括号里的除法,再算中括号里的加法,最后算括号外的乘法.
点评:此题考查了分数、小数四则混合运算的顺序,注意要括号的运算顺序.