递等式计算(能简算的要简算)4.65-2.55-1.456.4÷(0.3×2+0.2)201×6.5-6.52.2×0.25+2.8×0.25.

发布时间:2020-07-31 06:14:05

递等式计算(能简算的要简算) 4.65-2.55-1.456.4÷(0.3×2+0.2)201×6.5-6.52.2×0.25+2.8×0.25.

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解;①4.65-2.55-1.45,
=4.65-(2.55+1.45),
=4.65-4,
=0.65;

②6.4÷(0.3×2+0.2),
=6.4÷(0.6+0.2),
=6.4÷0.8,
=8;

③201×6.5-6.5,
=6.5×(201-1),
=0.65×200,
=130;

④2.2×0.25+2.8×0.25,
=0.25×(2.2+2.8),
=0.25×5,
=1.25.
解析分析:①4.65-2.55-1.45根据一个数连续减去两个数等于这个数减去这两个数的和计算简便,变成4.65-(2.55+1.45);②按四则运算的运算顺序,先算括号里的0.3×2,再算括号里的加,最后算除;③201×6.5-6.5利用乘法的分配律变成6.5×(201-1)计算简便;④2.2×0.25+2.8×0.25利用乘法的分配律变成0.25×(2.2+2.8)计算简便.

点评:考查了运算定律与简便运算,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.
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