Question

17．計(jì)算
①2.84+5.6+6.16+4.4
②$\frac{5}{9}$×[$\frac{3}{4}$-（$\frac{7}{16}$-$\frac{1}{4}$）]
③3.83×5.7-38.3×0.47．

Answer 1

分析 ①可運(yùn)用加法交換律和結(jié)合律簡便計(jì)算，
②先算小括號(hào)的減法，再算中括號(hào)的減法，最后算乘法，
③先把38.3×0.47變成3.83×4.7，再用乘法分配律簡算．

解答 解：①2.84+5.6+6.16+4.4
=（2.84+6.16）+（5.6+4.4）
=9+10
=19

②$\frac{5}{9}$×[$\frac{3}{4}$-（$\frac{7}{16}$-$\frac{1}{4}$）]
=$\frac{5}{9}$×[$\frac{3}{4}$-（$\frac{7}{16}$-$\frac{4}{16}$）]
=$\frac{5}{9}$×[$\frac{3}{4}$-$\frac{3}{16}$]
=$\frac{5}{9}$×[$\frac{12}{16}$$-\frac{3}{16}$]
=$\frac{5}{9}$×$\frac{9}{16}$
=$\frac{5}{16}$

③3.83×5.7-38.3×0.47
=3.83×5.7-3.83×4.7
=3.83×（5.7-4.7）
=3.83×1
=3.83

點(diǎn)評(píng) 此題考查小數(shù)和分?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．