2026年学法大视野七年级数学上册人教版第39页答案
1. 计算:$\frac{5}{31}×(-\frac{2}{9})×(-\frac{31}{15})×(-\frac{9}{2}).$

答案

解:原式$=-\frac{5}{31}×\frac{2}{9}×\frac{31}{15}×\frac{9}{2}$
$=-(\frac{5}{31}×\frac{31}{15})×(\frac{2}{9}×\frac{9}{2})$
$=-\frac{1}{3}×1$
$=-\frac{1}{3}.$
2. 计算：$(\dfrac{1}{4} - \dfrac{1}{6} + \dfrac{1}{24}) × (-48).$

答案

2. 解:原式$=\frac{1}{4}×(-48)-\frac{1}{6}×(-48)+\frac{1}{24}×(-48)$
$=-12+8-2$
$=-6.$
3. 计算：$4×(-\dfrac{27}{7})-3×(-\dfrac{27}{7})-6×\dfrac{27}{7}.$

答案

3. 解:原式$=-\frac{27}{7}×(4-3+6)=-\frac{27}{7}×7=-27.$
4. 计算：$(\dfrac{1}{6} - \dfrac{2}{7} + \dfrac{2}{3}) ÷ (-\dfrac{5}{42}).$

答案

解:原式$=(\frac{1}{6}-\frac{2}{7}+\frac{2}{3})×(-\frac{42}{5})$
$=\frac{1}{6}×(-\frac{42}{5})-\frac{2}{7}×(-\frac{42}{5})+\frac{2}{3}×(-\frac{42}{5})$
$=-\frac{7}{5}+\frac{12}{5}-\frac{28}{5}$
$=-\frac{23}{5}.$
5. 计算：$-\dfrac{3}{8} ÷ \dfrac{3}{5} × \dfrac{5}{3}$

答案

解:原式$=-\frac{3}{8}×\frac{5}{3}×\frac{5}{3}=-\frac{25}{24}.$
6. 计算：$-1^2 - (-\dfrac{1}{2})^3 ÷ 4.$

答案

解:原式$=-1-(-\frac{1}{8})÷4$
$=-1+\frac{1}{8}×\frac{1}{4}$
$=-1+\frac{1}{32}$
$=-\frac{31}{32}.$
7.计算:$(-24)÷(\dfrac{1}{3}-\dfrac{1}{8}-\dfrac{1}{6}).$

答案

7. 解:原式$=-24÷\frac{1}{24}=-24×24=-576.$