Question

20．計算下面各題，能簡算的要簡算．
（$\frac{7}{11}$+$\frac{3}{8}$）×88             
$\frac{7}{11}$×$\frac{8}{21}$×$\frac{11}{4}$
$\frac{2}{7}$+$\frac{1}{13}$×$\frac{2}{7}$
$\frac{4}{5}$+$\frac{4}{7}$×$\frac{7}{8}$．

Answer 1

分析 ①用乘法分配律計算．
②先約分再計算．
③用乘法分配律計算．
④先算乘法，再通分計算．

解答 解：①（$\frac{7}{11}$+$\frac{3}{8}$）×88 
=88×$\frac{7}{11}$+$\frac{3}{8}$×88
=56+33
=89

②$\frac{7}{11}$×$\frac{8}{21}$×$\frac{11}{4}$
=$\frac{7}{11}$×$\frac{11}{4}$×$\frac{8}{21}$
=$\frac{7}{4}×\frac{8}{21}$
=$\frac{2}{3}$

③$\frac{2}{7}$+$\frac{1}{13}$×$\frac{2}{7}$
=（1+$\frac{1}{13}$）×$\frac{2}{7}$
=$\frac{14}{13}×\frac{2}{7}$
=$\frac{4}{13}$

④$\frac{4}{5}$+$\frac{4}{7}$×$\frac{7}{8}$
=$\frac{4}{5}+\frac{1}{2}$
=$\frac{8}{10}+\frac{5}{10}$
=$\frac{13}{10}$

點評 本題主要考查分數(shù)四則混合運算的計算順序．