1. 有下列算式:
①$(-24)÷ (-8)=-3$;
②$(+32)÷ (-8)=-4$;
③$\left(-\dfrac{4}{5}\right)÷ \left(-\dfrac{4}{5}\right)=1$;
④$\left(-3\dfrac{3}{4}\right)÷ (-1.25)=-3$.
其中计算正确的个数是( )
A.1
B.2
C.3
D.4
①$(-24)÷ (-8)=-3$;
②$(+32)÷ (-8)=-4$;
③$\left(-\dfrac{4}{5}\right)÷ \left(-\dfrac{4}{5}\right)=1$;
④$\left(-3\dfrac{3}{4}\right)÷ (-1.25)=-3$.
其中计算正确的个数是( )
A.1
B.2
C.3
D.4
答案:
B
2. 计算$-1÷ 3× \dfrac{1}{3}$的结果是( )
A.$-1$
B.1
C.$-\dfrac{1}{9}$
D.$\dfrac{1}{9}$
A.$-1$
B.1
C.$-\dfrac{1}{9}$
D.$\dfrac{1}{9}$
答案:
C
3. 完成下表:

答案:
从左到右,从上到下依次填:1 1 6 6 -18 -18 0 0
4. 填空:
(1)$(-36)÷ 3=$______.
(2)$\left(-\dfrac{4}{5}\right)÷ \left(-\dfrac{2}{5}\right)=$______.
(3)$0÷ \left(-\dfrac{7}{12}\right)=$______.
(4)$(-18)÷ 6× \dfrac{1}{2}=$______.
(1)$(-36)÷ 3=$______.
(2)$\left(-\dfrac{4}{5}\right)÷ \left(-\dfrac{2}{5}\right)=$______.
(3)$0÷ \left(-\dfrac{7}{12}\right)=$______.
(4)$(-18)÷ 6× \dfrac{1}{2}=$______.
答案:
(1)-12
(2)2
(3)0
(4)$-\frac{3}{2}$
(1)-12
(2)2
(3)0
(4)$-\frac{3}{2}$
5. 计算:
(1)$-2÷ \dfrac{5}{6}× \left(-\dfrac{6}{5}\right)$.
(2)$(-510)÷ (+34)÷ (-0.125)$.
(3)$2\dfrac{1}{12}÷ \left(-1\dfrac{1}{4}\right)÷ \left(-1\dfrac{2}{3}\right)$.
(4)$(-81)÷ 2× \dfrac{1}{4}× \left(-\dfrac{2}{9}\right)$.
(1)$-2÷ \dfrac{5}{6}× \left(-\dfrac{6}{5}\right)$.
(2)$(-510)÷ (+34)÷ (-0.125)$.
(3)$2\dfrac{1}{12}÷ \left(-1\dfrac{1}{4}\right)÷ \left(-1\dfrac{2}{3}\right)$.
(4)$(-81)÷ 2× \dfrac{1}{4}× \left(-\dfrac{2}{9}\right)$.
答案:
解:
(1)原式$=-2×\frac{6}{5}×(-\frac{6}{5})=\frac{72}{25}$.
(2)原式$=15×8=120$.
(3)原式$=\frac{25}{12}×\frac{4}{5}×\frac{3}{5}=1$.
(4)原式$=81×\frac{1}{2}×\frac{1}{4}×\frac{2}{9}=\frac{9}{4}$.
(1)原式$=-2×\frac{6}{5}×(-\frac{6}{5})=\frac{72}{25}$.
(2)原式$=15×8=120$.
(3)原式$=\frac{25}{12}×\frac{4}{5}×\frac{3}{5}=1$.
(4)原式$=81×\frac{1}{2}×\frac{1}{4}×\frac{2}{9}=\frac{9}{4}$.
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