基础 主干落实 筑牢根基 答案 P235

答案
【新知要点】
正 负 相除 0 0 倒数
【对点小练】
C
正 负 相除 0 0 倒数
【对点小练】
C
【典例1】(教材再开发·P53例4拓展)计算:
(1)$(-54)÷ 9$;
(2)$4\dfrac{1}{3}÷ (-2\dfrac{1}{6})$;
(3)$-1÷ (-2\dfrac{1}{5})$;
(4)$(-3)÷ (-1.5)÷ (-2)$。
有理数的除法
(1)$(-54)÷ 9$;
(2)$4\dfrac{1}{3}÷ (-2\dfrac{1}{6})$;
(3)$-1÷ (-2\dfrac{1}{5})$;
(4)$(-3)÷ (-1.5)÷ (-2)$。
有理数的除法
答案
(1)原式$=-6$;
(2)原式$=\dfrac{13}{3}÷ (-\dfrac{13}{6})$
$=\dfrac{13}{3}× (-\dfrac{6}{13})$
$=-2$;
(3)原式$=-1÷ (-\dfrac{11}{5})$
$=1× \dfrac{5}{11}$
$=\dfrac{5}{11}$;
(4)原式$=2÷ (-2)$
$=-1$。
(2)原式$=\dfrac{13}{3}÷ (-\dfrac{13}{6})$
$=\dfrac{13}{3}× (-\dfrac{6}{13})$
$=-2$;
(3)原式$=-1÷ (-\dfrac{11}{5})$
$=1× \dfrac{5}{11}$
$=\dfrac{5}{11}$;
(4)原式$=2÷ (-2)$
$=-1$。
1.(2025·泸州期中)下列把除法转换为乘法的过程中正确的是(
A.$\frac{1}{3} ÷ (-4) = (-\frac{1}{3}) × 4$
B.$(-3) ÷ (-6) = (-6) × (-\frac{1}{3})$
C.$1 ÷ (-4) = 1 × (-\frac{1}{4})$
D.$(-3) ÷ 4 = 3 × \frac{1}{4}$
C
)A.$\frac{1}{3} ÷ (-4) = (-\frac{1}{3}) × 4$
B.$(-3) ÷ (-6) = (-6) × (-\frac{1}{3})$
C.$1 ÷ (-4) = 1 × (-\frac{1}{4})$
D.$(-3) ÷ 4 = 3 × \frac{1}{4}$
答案
C
2. 两数的商是$-\dfrac{5}{16}$,被除数是$-2\dfrac{1}{2}$,则除数是
8
。答案
【解析】$-2\dfrac{1}{2}÷ (-\dfrac{5}{16})$
$=\dfrac{5}{2}÷ \dfrac{5}{16}$
$=\dfrac{5}{2}× \dfrac{16}{5}$
$=8$.
答案:8
$=\dfrac{5}{2}÷ \dfrac{5}{16}$
$=\dfrac{5}{2}× \dfrac{16}{5}$
$=8$.
答案:8
3.计算:
(1)$0÷(-2)$.
(2)$(-\dfrac{22}{7})÷11$.
(3)$1÷(-\dfrac{22}{7})$.
(4)$(-20)÷[(-\dfrac{2}{3})÷(-\dfrac{5}{6})]$.
(1)$0÷(-2)$.
(2)$(-\dfrac{22}{7})÷11$.
(3)$1÷(-\dfrac{22}{7})$.
(4)$(-20)÷[(-\dfrac{2}{3})÷(-\dfrac{5}{6})]$.
答案
【解析】(1)$0÷ (-2)=0$.
(2)$(-\dfrac{22}{7})÷ 11$
$=-\dfrac{22}{7}× \dfrac{1}{11}$
$=-\dfrac{2}{7}$.
(3)$1÷ (-\dfrac{22}{7})$
$=-1× \dfrac{7}{22}$
$=-\dfrac{7}{22}$.
(4)$(-20)÷ [(-\dfrac{2}{3})÷ (-\dfrac{5}{6})]$
$=-20÷ (\dfrac{2}{3}× \dfrac{6}{5})$
$=-20÷ \dfrac{4}{5}$
$=-20× \dfrac{5}{4}$
$=-25$.
(2)$(-\dfrac{22}{7})÷ 11$
$=-\dfrac{22}{7}× \dfrac{1}{11}$
$=-\dfrac{2}{7}$.
(3)$1÷ (-\dfrac{22}{7})$
$=-1× \dfrac{7}{22}$
$=-\dfrac{7}{22}$.
(4)$(-20)÷ [(-\dfrac{2}{3})÷ (-\dfrac{5}{6})]$
$=-20÷ (\dfrac{2}{3}× \dfrac{6}{5})$
$=-20÷ \dfrac{4}{5}$
$=-20× \dfrac{5}{4}$
$=-25$.
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