计算下面各题,能用简便方法计算要用简便方法计算. (1)13.92-(1.19+9.92)-2.81(2)(+-)×30(3)55×66÷(11×11)(4)40.2-4÷80×2.4(5)×[÷(×)](6)×2002.
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11解:(1)13.92-(1.19+9.92)-2.81,
=13.92-1.19-9.92-2.81,
=(13.92-9.92)-(1.19+2.81),
=4-4,
=0;
(2)(+-)×30,
=×30+×30-×30,
=12+5-4,
=13;
(3)55×66÷(11×11),
=55×66÷11÷11,
=(55÷11)×(66÷11),
=5×6,
=30;
(4)40.2-4÷80×2.4,
=40.2-0.05×2.4,
=40.2-0.12,
=40.08;
(5)×[÷(×)],
=×[÷],
=×,
=;
(6)×2002,
=×(2001+1),
=×2001+×1,
=2000+,
=2000.
解析分析:(1)根据减法的性质简算;
(2)运用乘法分配律简算;
(3)根据除法的性质简算;
(4)先算除法,再算除法,最后算减法;
(5)先算小括号里面的乘法,再算中括号里面的除法,最后算括号外的除法;
(6)先把2002分解成(2001+1),再运用乘法分配律简算.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.