Question

14．能簡(jiǎn)算的要簡(jiǎn)算
1.2-0.5×1.8÷0.9           
8×7×1.25
（$\frac{3}{8}$-$\frac{3}{8}$÷$\frac{8}{3}$）×$\frac{16}{9}$          
$\frac{3}{5}$×8.8+0.6×$\frac{1}{5}$+60%

Answer 1

分析 ①先算乘法再算除法，最后算減法；
②運(yùn)用乘法交換律和結(jié)合律簡(jiǎn)算；
③先算除法，再用乘法分配律簡(jiǎn)算；
④先把0.6，60%變成分?jǐn)?shù)，再用乘法分配律簡(jiǎn)算．

解答 解：①1.2-0.5×1.8÷0.9
=1.2-0.9÷0.9
=1.2-1
=0.2           

②8×7×1.25
=（8×1.25）×7
=10×7
=70

③（$\frac{3}{8}$-$\frac{3}{8}$÷）×$\frac{16}{9}$  
=（$\frac{3}{8}$-$\frac{3}{8}$）×$\frac{16}{9}$
=（$\frac{3}{8}$-）×$\frac{16}{9}$
=$\frac{3}{8}$×$\frac{16}{9}$-$\frac{9}{64}$×$\frac{16}{9}$
=$\frac{2}{3}$$-\frac{1}{4}$
=$\frac{8}{12}$$-\frac{3}{12}$
=$\frac{5}{12}$       

④$\frac{3}{5}$×8.8+0.6×$\frac{1}{5}$+60%
=$\frac{3}{5}$×8.8+$\frac{3}{5}$×$\frac{1}{5}$+$\frac{3}{5}$
=$\frac{3}{5}$×（8.8$+\frac{1}{5}$+1）
=$\frac{3}{5}$×10
=6

點(diǎn)評(píng) 此題考查小數(shù)、分?jǐn)?shù)四則混合運(yùn)算順序和靈活運(yùn)用運(yùn)算定律，分析數(shù)據(jù)找到正確的計(jì)算方法．