题目内容

用简便的方法计算下面各题
4,5×0.9+5.5×0.9     
7.69×101    
2.5×(7.2×0.04)
72×l.25    
0.26×10.1-0.26×0.1    
0.25+39×0.25.
分析:(1)根据乘法分配律进行计算;
(2)根据乘法分配律进行计算
(3)根据乘法交换律和结合律进行计算;
(4)根据乘法交换律和结合律进行计算.
(5)根据乘法分配律进行计算
(6)根据乘法分配律进行计算
解答:解:(1)4.5×0.9+5.5×0.9,
=(4.5+5.5)×0.9,
=10×0.9,
=9;

(2)7.69×101,
=7.69×(100+1),
=7.69×100+7.69×1,
=769+7.69,
=776.69;

(3)2.5×(7.2×0.04),
=7.2×(2.5×0.04),
=7.2×0.1,
=0.72;

(4)72×l.25,
=(8×9)×1.25,
=(8×1.25)×9,
=10×9,
=90;

(5)0.26×10.1-0.26×0.1,
=0.26×(10.1-0.1),
=0.26×10,
=2.6;

(6)0.25+39×0.25,
=0.25×(1+39),
=0.25×40,
=10.
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.
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