Question

7．下面各題怎樣算簡(jiǎn)便就怎樣算，要寫出主要的計(jì)算過程．
4.6×99+4.6                       
（$\frac{4}{5}$+$\frac{1}{4}$）×$\frac{1}{3}$×70%
4×0.8×2.5×12.5                       
$\frac{1}{4}$×$\frac{1}{5}$÷$\frac{1}{5}$×$\frac{1}{4}$．

Answer 1

分析 ①運(yùn)用乘法的分配律進(jìn)行計(jì)算即可．
②先計(jì)算小括號(hào)內(nèi)部的，再計(jì)算括號(hào)外面的．
③運(yùn)用乘法的交換律及結(jié)合律進(jìn)行計(jì)算即可．
④按四則混合運(yùn)算的順序，從左邊依次計(jì)算即可．

解答 解：①4.6×99+4.6 
=4.6×（99+1）
=4.6×100
=460
                      
②（$\frac{4}{5}$+$\frac{1}{4}$）×$\frac{1}{3}$×70%
=$\frac{21}{20}$×$\frac{1}{3}$×$\frac{7}{10}$
=$\frac{49}{200}$


③4×0.8×2.5×12.5 
=（4×2.5）×（12.5×0.8）
=10×10
=100
                      
④$\frac{1}{4}$×$\frac{1}{5}$÷$\frac{1}{5}$×$\frac{1}{4}$
=$\frac{1}{4}$×$\frac{1}{4}$
=$\frac{1}{16}$

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．