《2025年课堂点睛七年级数学上册人教版安徽专版》

1. 计算：
(1)$(-2)× (-0.125)× 9× (-8)$；
(2)$-1\frac {5}{7}× \frac {5}{6}× |-1\frac {2}{5}|× 1.2$；
(3)$(-1.25)× 2.5÷ 5÷ \frac {1}{4}× 8$.

答案：
(1)解:原式=(-2)×9×[(-0.125)×(-8)]=-18×1=-18.
(2)解:原式=$-\frac{12}{7}×\frac{5}{6}×\frac{7}{5}×\frac{6}{5}=(-\frac{12}{7}×\frac{7}{5})×(\frac{5}{6}×\frac{6}{5})=-\frac{12}{5}×1=-\frac{12}{5}$.
(3)解:原式=$-\frac{5}{4}×\frac{5}{2}×\frac{1}{5}×4×8=(-\frac{5}{4}×4)×(\frac{5}{2}×\frac{1}{5}×8)=-20$.

2. 计算：
(1)$(-36)× (-\frac {4}{9}+\frac {5}{6}-\frac {7}{12})$；
(2)$(\frac {2}{9}-\frac {1}{4}-\frac {1}{18})÷ (-\frac {1}{36})$.

答案：
(1)解:原式=$(-36)×(-\frac{4}{9})+(-36)×\frac{5}{6}+(-36)×(-\frac{7}{12})=16+(-30)+21=7$.
(2)解:原式=$(\frac{2}{9}-\frac{1}{4}-\frac{1}{18})×(-36)=(-8)+9+2=3$.

3. 计算：
(1)$999× 118\frac {4}{5}+999× (-\frac {1}{5})-999× 18\frac {3}{5}$；
(2)$(-8)× 2\frac {1}{4}-\frac {9}{4}÷ (-\frac {1}{8})$；
(3)$-3.14× 35.2+6.28× (-23.3)-1.57× 36.4$.

答案：
(1)解:原式=$999×(118\frac{4}{5}-\frac{1}{5}-18\frac{3}{5})=999×100=99900$.
(2)解:原式=$-8×\frac{9}{4}-\frac{9}{4}×(-8)=\frac{9}{4}×[-8-(-8)]=0$.
(3)解:原式=$-6.28×17.6+6.28×(-23.3)-6.28×9.1=-6.28×(17.6+23.3+9.1)=-6.28×50=-314$.