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我会巧算. 1.2×0.4+1.3×0.4×0.27.2×0.3+28×0.030.25×0.56×0.48×0.25×0.56×0.432.8+5.6+7.275.2-66.9-5.2.

编辑:chaxungu时间:2026-04-27 11:18:56分类:小学数学题库

我会巧算.
1.2×0.4+1.3×0.4(1.25+0.36)×0.27.2×0.3+28×0.030.25×0.56×0.4
8×(2.5+0.125)0.25×0.56×0.432.8+5.6+7.275.2-66.9-5.2.
解:
(1)1.2×0.4+1.3×0.4,
=(1.2+1.3)×0.4,
=2.5×0.4,
=1;

(2)(1.25+0.36)×0.2,
=1.25×0.2+0.36×0.2,
=0.25+0.072,
=0.322;

(3)7.2×0.3+28×0.03,
=72×0.03+28×0.03,
=(72+28)×0.03,
=100×0.03,
=3;

(4)0.25×0.56×0.4,
=0.25×0.4×0.56,
=0.1×0.56,
=0.056;

(5)8×(2.5+0.125),
=8×2.5+8×0.125,
=20+1,
=21;

(6)0.25×0.56×0.4,
=0.25×0.4×0.56,
=0.1×0.56,
=0.056;

(7)32.8+5.6+7.2,
=32.8+7.2+5.6,
=40+5.6,
=45.6;

(8)75.2-66.9-5.2,
=75.2-5.2-66.9,
=70-66.9,
=3.1.
分析:(1)、(2)、(3)和(5)根据乘法分配律进行简算;
(4)和(6)根据乘法交换律进行简算;
(7)根据加法交换律进行简算;
(8)根据连减的性质进行简算.
点评:完成本题要注意分析式中数据,运用合适的简便方法计算.