17.計算題:
(1)$\frac{1}{8}$×56×$\frac{2}{7}$
(2)$\frac{5}{9}$×$\frac{3}{5}$÷$\frac{6}{7}$
(3)12×($\frac{1}{2}$+$\frac{3}{4}$)
(4)$\frac{7}{8}$÷($\frac{5}{6}$×$\frac{2}{5}$)
(5)$\frac{3}{5}$÷$\frac{1}{10}$÷$\frac{2}{3}$.
分析 (1)、(2)、(5)按照從左向右的順序進(jìn)行計算;
(3)根據(jù)乘法分配律進(jìn)行簡算;
(4)先算乘法,再算除法.
解答 解:(1)$\frac{1}{8}$×56×$\frac{2}{7}$
=7×$\frac{2}{7}$
=2;
(2)$\frac{5}{9}$×$\frac{3}{5}$÷$\frac{6}{7}$
=$\frac{1}{3}$÷$\frac{6}{7}$
=$\frac{7}{18}$;
(3)12×($\frac{1}{2}$+$\frac{3}{4}$)
=12×$\frac{1}{2}$+12×$\frac{3}{4}$
=6+9
=15;
(4)$\frac{7}{8}$÷($\frac{5}{6}$×$\frac{2}{5}$)
=$\frac{7}{8}$÷$\frac{1}{3}$
=$\frac{21}{8}$;
(5)$\frac{3}{5}$÷$\frac{1}{10}$÷$\frac{2}{3}$
=6÷$\frac{2}{3}$
=9.
點評 考查了運算定律與簡便運算,四則混合運算.注意運算順序和運算法則,靈活運用所學(xué)的運算定律簡便計算.