Question

12．脫式計算，能簡便計算的要使用簡便方法計算．
$\frac{4}{9}$×$\frac{3}{7}$+$\frac{4}{9}$×$\frac{4}{7}$               37×$\frac{5}{36}$             （$\frac{3}{4}$+$\frac{4}{5}$）×40
2-$\frac{5}{6}$÷$\frac{5}{6}$                  $\frac{5}{12}$÷$\frac{5}{6}$×$\frac{4}{7}$            $\frac{7}{12}$÷$\frac{7}{9}$÷$\frac{5}{4}$．

Answer 1

分析 ①②③運用乘法的分配律進行計算即可．
④根據(jù)四則混合運算的運算順序計算即可．

解答 解：①$\frac{4}{9}$×$\frac{3}{7}$+$\frac{4}{9}$×$\frac{4}{7}$ 
=$\frac{4}{9}$×（$\frac{3}{7}+\frac{4}{7}$）
=$\frac{4}{9}$×1
=$\frac{4}{9}$

             
②37×$\frac{5}{36}$
=（36+1）×$\frac{5}{36}$
=36×$\frac{5}{36}$+1×$\frac{5}{36}$
=5$+\frac{5}{36}$
=5$\frac{5}{36}$

            
③（$\frac{3}{4}$+$\frac{4}{5}$）×40
=40×$\frac{3}{4}$+40×$\frac{4}{5}$
=30+32
=62

④2-$\frac{5}{6}$÷$\frac{5}{6}$ 
=2-1
=1
                
⑤$\frac{5}{12}$÷$\frac{5}{6}$×$\frac{4}{7}$
=$\frac{5}{12}×\frac{6}{5}$×$\frac{4}{7}$
=$\frac{1}{2}×\frac{4}{7}$
=$\frac{2}{7}$

            
⑥$\frac{7}{12}$÷$\frac{7}{9}$÷$\frac{5}{4}$
=$\frac{7}{12}×\frac{9}{7}×\frac{4}{5}$
=$\frac{3}{5}$

點評 完成本題要注意分析式中數(shù)據(jù)，運用合適的簡便方法計算．