Question

19．脫式計(jì)算（能簡便計(jì)算的要簡便計(jì)算）．
4.15×43%+85×0.43                      
$\frac{7}{9}$÷$\frac{11}{5}$+$\frac{2}{9}$×$\frac{5}{11}$．

Answer 1

分析 ①用乘法分配律計(jì)算即可，如a×（b+c）=ab+ac．
②把除法轉(zhuǎn)化為乘法，再用乘法分配律計(jì)算即可．

解答 解：①4.15×43%+85×0.43 
=（4.15+85）×0.43 
=89.15×0.43
=38.3345

②$\frac{7}{9}÷\frac{11}{5}+\frac{2}{9}×\frac{5}{11}$
=$\frac{7}{9}×\frac{5}{11}+\frac{2}{9}×\frac{5}{11}$
=$\frac{5}{11}$×（$\frac{2}{9}+\frac{7}{9}$）
=$\frac{5}{11}$

點(diǎn)評(píng) 本題主要考查分?jǐn)?shù)四則混合運(yùn)算的計(jì)算順序，能簡便計(jì)算的要簡便計(jì)算．