《2025年新编基础训练七年级数学上册人教版》

1. 计算：
(1) $ 4\frac{3}{4}-(+3.85)-3\frac{1}{4}+(-3.15) $；
(2) $ \left|-2\frac{1}{5}\right|-(-2.5)-1-\left|1-2\frac{1}{5}\right| $。

答案： 1.解:
(1)$4\frac {3}{4}-(+3.85)-3\frac {1}{4}+(-3.15)$
$=(4\frac {3}{4}-3\frac {1}{4})+(-3.85-3.15)$
$=1\frac {1}{2}-7$
$=-5.5.$
(2)$|-2\frac {1}{5}|-(-2.5)-1-|1-2\frac {1}{5}|$
$=2\frac {1}{5}+2.5-1-2\frac {1}{5}+1$
$=2\frac {1}{5}+2.5-1+(-2\frac {1}{5})+1$
$=2.5.$

2. 计算：
(1) $ \left(-2\frac{1}{7}\right)÷ (-1.2)× \left(-1\frac{2}{5}\right) $；
(2) $ (-3)÷ \left(-1\frac{3}{4}\right)× \frac{3}{4}÷ \frac{3}{7} $。

答案： 2.解:
(1)$(-2\frac {1}{7})÷(-1.2)×(-1\frac {2}{5})$
$=(-\frac {15}{7})×(-\frac {5}{6})×(-\frac {7}{5})$
$=-\frac {5}{2}.$
(2)$(-3)÷(-1\frac {3}{4})×\frac {3}{4}÷\frac {3}{7}$
$=3÷\frac {7}{4}×\frac {3}{4}×\frac {7}{3}$
$=3×\frac {4}{7}×\frac {3}{4}×\frac {7}{3}$
$=3.$

3. 计算：
(1) $ -3^{2}× \left(-\frac{1}{3}\right)^{2}+\left(\frac{3}{4}-\frac{1}{6}+\frac{3}{8}\right)× (-24) $；
(2) $ \left(-\frac{3}{4}+\frac{5}{9}-\frac{7}{12}\right)÷ \frac{1}{36}-(-3 - 1)^{2}× \left(-1^{2}+1\frac{7}{8}\right) $。

答案： 3.解:
(1)$-3^{2}×(-\frac {1}{3})^{2}+(\frac {3}{4}-\frac {1}{6}+\frac {3}{8})×(-24)$
$=-9×\frac {1}{9}-24×\frac {3}{4}+24×\frac {1}{6}-24×\frac {3}{8}$
$=-1-18+4-9$
$=-24.$
(2)$(-\frac {3}{4}+\frac {5}{9}-\frac {7}{12})÷\frac {1}{36}-(-3-1)^{2}×(-1^{2}+1\frac {7}{8})$
$=(-\frac {3}{4}+\frac {5}{9}-\frac {7}{12})×36-(-4)^{2}×(-1+1\frac {7}{8})$
$=-\frac {3}{4}×36+\frac {5}{9}×36-\frac {7}{12}×36-16×\frac {7}{8}$
$=-27+20-21-14$
$=-42.$

4. 计算：
(1) $ -2^{2}× 0.125-\left[4÷ \left(-\frac{2}{3}\right)^{2}-\frac{1}{2}\right]+(-1)^{2024} $；
(2) $ -3^{2}-\left[8÷ (-2)^{3}+\frac{1}{2}\right]+3÷ 2× \frac{1}{2} $。

答案： 4.解:
(1)$-2^{2}×0.125-[4÷(-\frac {2}{3})^{2}-\frac {1}{2}]+(-1)^{2024}$
$=-4×\frac {1}{8}-(4×\frac {9}{4}-\frac {1}{2})+1$
$=-\frac {1}{2}-9+\frac {1}{2}+1$
$=-8.$
(2)$-3^{2}-[8÷(-2)^{3}+\frac {1}{2}]+3÷2×\frac {1}{2}$
$=-9-[8÷(-8)+\frac {1}{2}]+3×\frac {1}{2}×\frac {1}{2}$
$=-9-(-1+\frac {1}{2})+\frac {3}{4}$
$=-9+\frac {1}{2}+\frac {3}{4}$
$=-\frac {31}{4}.$