Question

11．計(jì)算下面各題，怎樣簡便就怎樣算
①$\frac{4}{9}$×$\frac{11}{21}$+$\frac{5}{9}$×$\frac{11}{21}$                           
②$\frac{14}{15}$×（$\frac{4}{21}$+$\frac{3}{14}$）÷$\frac{7}{15}$
③4.3×6.7+0.67×67-6.7                    
④2.5×32×0.125．

Answer 1

分析 ①運(yùn)用乘法的分配律進(jìn)行簡算；
②先算小括號里的加法，再把除以$\frac{7}{15}$化成乘法$\frac{15}{7}$，運(yùn)用乘法的交換律進(jìn)行簡算；
③運(yùn)用乘法的分配律進(jìn)行簡算；
④2.5×32×0.125，把32拆分為4×8，再運(yùn)用乘法的交換律、結(jié)合律簡算．

解答 解：①$\frac{4}{9}$×$\frac{11}{21}$+$\frac{5}{9}$×$\frac{11}{21}$ 
=（$\frac{4}{9}$+$\frac{5}{9}$）×$\frac{11}{21}$ 
=1×$\frac{11}{21}$
=$\frac{11}{21}$；

②$\frac{14}{15}$×（$\frac{4}{21}$+$\frac{3}{14}$）÷$\frac{7}{15}$
=$\frac{14}{15}$×$\frac{17}{42}$÷$\frac{7}{15}$
=$\frac{14}{15}$×$\frac{17}{42}$×$\frac{15}{7}$
=$\frac{14}{15}$×$\frac{15}{7}$×$\frac{17}{42}$
=2×$\frac{17}{42}$
=$\frac{17}{21}$；

③4.3×6.7+0.67×67-6.7
=4.3×6.7+6.7×6.7-6.7
=（4.3+6.7-1）×6.7
=10×6.7
=67；

④2.5×32×0.125
=2.5×4×8×0.125
=（2.5×4）×（8×0.125）
=10×1
=10．

點(diǎn)評 此題考查了分?jǐn)?shù)、小數(shù)的簡算，注意分析算式中的數(shù)據(jù)，運(yùn)用恰當(dāng)?shù)倪\(yùn)算定律和性質(zhì)簡算．