1. 除以一个
不等于0
的数,等于乘这个数的
倒数
.
2. 两个不等于 0 的数相除,同号得
正
,异号得
负
,并把
绝对值
相除.0 除以任何一个
不等于0
的数,都得 0.
答案：1. 不等于0 倒数 2. 正 负 绝对值 不等于0
1. 计算$3÷(-\frac {1}{2})$的结果是 (
C
)
A.$\frac {3}{2}$
B.$-\frac {3}{2}$
C.-6
D.6
答案：C
解析：
解：$3÷(-\frac{1}{2}) = 3×(-2) = -6$
答案：C
2. 计算：
(1)$(-18)÷6;$
(2)$(-63)÷(-7);$
(3)$1÷(-9);$
(4)$0÷(-8);$
(5)$(-6.5)÷0.13;$
(6)$(-\frac {6}{5})÷(-\frac {2}{5}).$
答案：(1)-3 (2)9 (3)$-\frac{1}{9}$ (4)0 (5)-50 (6)3
解析：
(1)$(-18)÷6=-3$
(2)$(-63)÷(-7)=9$
(3)$1÷(-9)=-\frac{1}{9}$
(4)$0÷(-8)=0$
(5)$(-6.5)÷0.13=-50$
(6)$(-\frac{6}{5})÷(-\frac{2}{5})=3$
3. 计算：
(1)$12×(-\frac {4}{3})÷5;$
(2)$-10÷5×\frac {1}{5};$
(3)$-\frac {4}{3}×(-\frac {1}{6})÷(-\frac {7}{24});$
(4)$(-\frac {6}{5})÷(-1\frac {1}{2})-(-\frac {3}{4})×\frac {8}{5};$
(5)$(-35\frac {7}{11})÷7;$
(6)$(\frac {1}{7}+\frac {1}{3}-\frac {1}{5})÷(-\frac {1}{105}).$
答案：解:(1)原式$=-16÷ 5=-\frac{16}{5}$. (2)原式$=-10× \frac{1}{5}× \frac{1}{5}=-\frac{2}{5}$. (3)原式$=-\frac{4}{3}× \left(-\frac{1}{6}\right)× \left(-\frac{24}{7}\right)=-\frac{16}{21}$. (4)原式$=-\frac{6}{5}× \left(-\frac{2}{3}\right)+\frac{3}{4}× \frac{8}{5}=\frac{4}{5}+\frac{6}{5}=2$. (5)原式$=-\left(35+\frac{7}{11}\right)× \frac{1}{7}=-5-\frac{7}{11}× \frac{1}{7}=-5\frac{1}{11}$. (6)原式$=\frac{1}{7}× (-105)+\frac{1}{3}× (-105)-\frac{1}{5}× (-105)=-15-35+21=-29$.
解析：
(1)解:原式$=12×(-\frac{4}{3})÷5=-16÷5=-\frac{16}{5}$.
(2)解:原式$=-10×\frac{1}{5}×\frac{1}{5}=-2×\frac{1}{5}=-\frac{2}{5}$.
(3)解:原式$=-\frac{4}{3}×(-\frac{1}{6})×(-\frac{24}{7})=\frac{4}{18}×(-\frac{24}{7})=-\frac{96}{126}=-\frac{16}{21}$.
(4)解:原式$=(-\frac{6}{5})÷(-\frac{3}{2})+\frac{3}{4}×\frac{8}{5}=(-\frac{6}{5})×(-\frac{2}{3})+\frac{24}{20}=\frac{12}{15}+\frac{6}{5}=\frac{4}{5}+\frac{6}{5}=2$.
(5)解:原式$=(-35-\frac{7}{11})×\frac{1}{7}=-35×\frac{1}{7}-\frac{7}{11}×\frac{1}{7}=-5-\frac{1}{11}=-5\frac{1}{11}$.
(6)解:原式$=(\frac{1}{7}+\frac{1}{3}-\frac{1}{5})×(-105)=\frac{1}{7}×(-105)+\frac{1}{3}×(-105)-\frac{1}{5}×(-105)=-15-35+21=-29$.
