Question

9．下面各題怎樣簡便就怎樣算
99×$\frac{7}{100}$                              
$\frac{1}{4}$×64×$\frac{1}{8}$
$\frac{3}{5}$-$\frac{3}{5}$×$\frac{1}{3}$                      
$\frac{7}{2}$×$\frac{5}{8}$-$\frac{3}{2}$÷$\frac{8}{5}$．

Answer 1

分析 ①99×$\frac{7}{100}$，轉(zhuǎn)化為：（100-1）×$\frac{7}{100}$，運(yùn)用乘法分配律簡算；                            
②$\frac{1}{4}$×64×$\frac{1}{8}$，先約分再計算；
③$\frac{3}{5}$-$\frac{3}{5}$×$\frac{1}{3}$，先算乘法，再算減法；                    
④$\frac{7}{2}$×$\frac{5}{8}$-$\frac{3}{2}$÷$\frac{8}{5}$，把除數(shù)轉(zhuǎn)化為乘它的倒數(shù)，再運(yùn)用乘法分配律簡算；

解答 解：①99×$\frac{7}{100}$ 
=$（100-1）×\frac{7}{100}$
=$100×\frac{7}{100}-1×\frac{7}{100}$
=7$-\frac{7}{100}$
=$6\frac{93}{100}$；
                             
②$\frac{1}{4}$×64×$\frac{1}{8}$
=$16×\frac{1}{8}$
=2；

③$\frac{3}{5}$-$\frac{3}{5}$×$\frac{1}{3}$    
=$\frac{3}{5}-\frac{1}{5}$
=$\frac{2}{5}$；
                  
④$\frac{7}{2}$×$\frac{5}{8}$-$\frac{3}{2}$÷$\frac{8}{5}$
=$\frac{7}{2}×\frac{5}{8}-\frac{3}{2}×\frac{5}{8}$
=$（\frac{7}{2}-\frac{3}{2}）×\frac{5}{8}$
=2×$\frac{5}{8}$
=$\frac{5}{4}$．

點評 此題考查的目的是理解掌握分?jǐn)?shù)四則混合運(yùn)算的順序以及它們的計算法則，并且能夠靈活選擇簡便方法進(jìn)行計算．