Question

12．簡(jiǎn)便計(jì)算：
（4+0.8）×0.25   
0.7×9.9   
1.25×0.7×0.8   
25×3.2×0.125．

Answer 1

分析 ①根據(jù)乘法分配律進(jìn)行計(jì)算；
②把9.9寫成10-0.1，再根據(jù)乘法分配律進(jìn)行計(jì)算；
③根據(jù)乘法交換律計(jì)算；
④把3.2寫成0.4×8，再根據(jù)乘法結(jié)合律計(jì)算．

解答 解：①（4+0.8）×0.25   
=4×0.25+0.8×0.25
=1+0.2
=1.2

②0.7×9.9   
=0.7×（10-0.1）
=0.7×10-0.7×0.1
=7-0.07
=6.93

③1.25×0.7×0.8   
=1.25×0.8×0.7
=1×0.7
=0.7

④25×3.2×0.125
=25×0.4×8×0.125
=（25×0.4）×（8×0.125）
=10×1
=10

點(diǎn)評(píng) 完成本題要注意分析式中數(shù)據(jù)，運(yùn)用合適的簡(jiǎn)便方法計(jì)算．