《2025年重点中学招生分班五年真题分类卷数学》

17. (2024 陕西 TYZ 元培班)$24×(\frac {7}{8}+1\frac {1}{4}-\frac {5}{12}-\frac {1}{2})÷\frac {29}{36}$

答案： 解:原式=$24×\left(\frac{7}{8}+\frac{5}{4}-\frac{5}{12}-\frac{1}{2}\right)×\frac{36}{29}$=$\left(24×\frac{7}{8}+24×\frac{5}{4}-24×\frac{5}{12}-24×\frac{1}{2}\right)×\frac{36}{29}$=(21+30-10-12)×$\frac{36}{29}$=29×$\frac{36}{29}$=36

18. (2024 陕西 TYZBH 学校)$4\% ×6+\frac {19}{25}×40\% +\frac {19}{25}×60\% $

答案： 解:原式=4%×6+$\frac{19}{25}$×(40%+60%)=$\frac{1}{25}×6+\frac{19}{25}×1$=$\frac{1}{25}×(6+19)$=1

19. (2024 陕西 TYZBH 学校)$(\frac {1}{2}+\frac {1}{4}+\frac {1}{6}+\frac {1}{8})-(\frac {1}{3}+\frac {1}{6}+\frac {1}{9}+\frac {1}{12})$

答案： 解:原式=$\frac{1}{2}×\left(1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}\right)-\frac{1}{3}×\left(1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}\right)$=$\left(\frac{1}{2}-\frac{1}{3}\right)×\left(1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}\right)$=$\frac{1}{6}×\frac{25}{12}$=$\frac{25}{72}$

20. (2024 陕西 GX3C)$\frac {11}{8}×(\frac {6}{7}-0.4)+\frac {22}{8}×\frac {1}{5}-1\frac {3}{8}×\frac {5}{7}$

答案： 解:原式=$\frac{11}{8}×\left(\frac{6}{7}-\frac{2}{5}\right)+\frac{11}{8}×\frac{2}{5}-\frac{11}{8}×\frac{5}{7}$=$\frac{11}{8}×\left(\frac{6}{7}-\frac{2}{5}+\frac{2}{5}-\frac{5}{7}\right)$=$\frac{11}{8}×\left(\frac{6}{7}-\frac{5}{7}\right)$=$\frac{11}{8}×\frac{1}{7}$=$\frac{11}{56}$

21. (2023 陕西 JDFZ)$\frac {5}{6}×\frac {2}{17}+\frac {5}{9}×\frac {8}{17}+\frac {5}{18}×\frac {12}{17}$

答案： 解:原式=$\frac{5}{17}×\frac{2}{6}+\frac{5}{17}×\frac{8}{9}+\frac{5}{17}×\frac{12}{18}$=$\frac{5}{17}×\left(\frac{2}{6}+\frac{8}{9}+\frac{12}{18}\right)$=$\frac{5}{17}×\frac{17}{9}$=$\frac{5}{9}$