Question

8．用簡(jiǎn)便方法計(jì)算下列各題：
8×6.39×1.25      
8.4×0.25         
3.7×0.25+0.25×0.3      
98×1.5．

Answer 1

分析 ①根據(jù)乘法交換律及結(jié)合律計(jì)算；
②把8.4寫(xiě)成2.1×4，再根據(jù)乘法交換律及結(jié)合律計(jì)算；
③根據(jù)乘法分配律進(jìn)行計(jì)算；
④把98寫(xiě)成100-2，據(jù)乘法分配律進(jìn)行計(jì)算．

解答 解：①8×6.39×1.25
=（8×1.25）×6.39
=1000×6.39
=6390

②8.4×0.25         
=（2.1×4）×0.25
=2.1×（0.25×4）
=2.1×1
=2.1

③3.7×0.25+0.25×0.3
=0.25×（3.7+0.3）
=0.25×4
=1

④98×1.5
=（100-2）×1.5
=100×1.5-2×1.5
=150-3
=147

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．