Question

11．細(xì)心算
$\frac{1}{2}$+$\frac{1}{3}$+$\frac{1}{4}$                 
$\frac{7}{9}$-$\frac{2}{3}$+$\frac{2}{9}$                    
1-$\frac{1}{6}$-$\frac{5}{6}$．

Answer 1

分析 ①$\frac{1}{2}$+$\frac{1}{3}$+$\frac{1}{4}$，根據(jù)異分母分?jǐn)?shù)的加法，先通分，再按照同分母分?jǐn)?shù)加法的計(jì)算法則計(jì)算；                
②$\frac{7}{9}$-$\frac{2}{3}$+$\frac{2}{9}$，根據(jù)加、減法的運(yùn)算性質(zhì)簡算；                   
③1-$\frac{1}{6}$-$\frac{5}{6}$，根據(jù)減法的運(yùn)算性質(zhì)簡算．

解答 解：①$\frac{1}{2}$+$\frac{1}{3}$+$\frac{1}{4}$  
=$\frac{6}{12}+\frac{4}{12}+\frac{3}{12}$
=$\frac{13}{12}$
=$1\frac{1}{12}$；
               
②$\frac{7}{9}$-$\frac{2}{3}$+$\frac{2}{9}$    
=$\frac{7}{9}+\frac{2}{9}-\frac{2}{3}$
=$1-\frac{2}{3}$
=$\frac{1}{3}$；
                
③1-$\frac{1}{6}$-$\frac{5}{6}$
=$1-（\frac{1}{6}+\frac{5}{6}）$
=1-1
=0．

點(diǎn)評(píng) 此題考查的目的是理解掌握分?jǐn)?shù)加、減法的計(jì)算法則，并且能夠靈活運(yùn)用加、減法的運(yùn)算性質(zhì)進(jìn)行簡便計(jì)算．