登录
1.(2024·宿迁)6 的倒数是 （
A.$\frac{1}{6}$
B.$-\frac{1}{6}$
C.6
D.$-6$
A
）A.$\frac{1}{6}$
B.$-\frac{1}{6}$
C.6
D.$-6$
答案
1.A
2. 下列计算，运用乘法结合律的是 （
A.$\frac{5}{3}×\frac{6}{7}=\frac{6}{7}×\frac{5}{3}$
B.$\frac{4}{5}×\frac{11}{12}×\frac{5}{4}=\frac{11}{12}×(\frac{4}{5}×\frac{5}{4})$
C.$\frac{5}{7}×13-\frac{5}{7}×6=\frac{5}{7}×(13-6)$
D.$\frac{3}{8}-\frac{4}{5}+\frac{5}{8}=(\frac{3}{8}+\frac{5}{8})-\frac{4}{5}$
B
）A.$\frac{5}{3}×\frac{6}{7}=\frac{6}{7}×\frac{5}{3}$
B.$\frac{4}{5}×\frac{11}{12}×\frac{5}{4}=\frac{11}{12}×(\frac{4}{5}×\frac{5}{4})$
C.$\frac{5}{7}×13-\frac{5}{7}×6=\frac{5}{7}×(13-6)$
D.$\frac{3}{8}-\frac{4}{5}+\frac{5}{8}=(\frac{3}{8}+\frac{5}{8})-\frac{4}{5}$
答案
2.B
3.(1)$-\dfrac{1}{5}$的倒数是
-5
；(2)$-1\dfrac{1}{3}$的倒数是$-\dfrac{3}{4}$
；(3)$-2.5$的倒数是$-\dfrac{2}{5}$
。答案
3.(1)$-5$ (2)$-\dfrac{3}{4}$ (3)$-\dfrac{2}{5}$
4.运用运算律填空：
[(-3)×2]×(-5)=(-3)×[
[(-3)×2]×(-5)=(-3)×[
2
×(-5)
].答案
4.2 (-5)
5. 计算：
(1)$(-25)×(-85)×(-4);$
(2)$1.6×(-1\dfrac{4}{5})×(-2.5)×(-\dfrac{3}{8});$
(3)$(\dfrac{1}{4}-\dfrac{1}{2}-\dfrac{1}{8})×16;$
(4)$(\dfrac{2}{9}-\dfrac{1}{3}-\dfrac{2}{27})×(-27).$
(1)$(-25)×(-85)×(-4);$
(2)$1.6×(-1\dfrac{4}{5})×(-2.5)×(-\dfrac{3}{8});$
(3)$(\dfrac{1}{4}-\dfrac{1}{2}-\dfrac{1}{8})×16;$
(4)$(\dfrac{2}{9}-\dfrac{1}{3}-\dfrac{2}{27})×(-27).$
答案
5.(1)$-8500$ (2)$-2.7$ (3)$-6$ (4)$5$
6.若一个数的倒数等于它本身，这样的数有 （
A.3个
B.2个
C.1个
D.0个
B
）A.3个
B.2个
C.1个
D.0个
答案
6.B
7. 在简便运算时，把$24×(-99\frac{47}{48})$变形成最合适的形式是（
A.$24×(-100+\frac{1}{48})$
B.$24×(-100-\frac{1}{48})$
C.$24×(-99-\frac{47}{48})$
D.$24×(-99+\frac{47}{48})$
A
）A.$24×(-100+\frac{1}{48})$
B.$24×(-100-\frac{1}{48})$
C.$24×(-99-\frac{47}{48})$
D.$24×(-99+\frac{47}{48})$
答案
7.A
8.若$2026×21=p$，则$-2026×20$的值可表示为（
A.$1-p$
B.$p+1$
C.$-p+2026$
D.$\frac{20}{21}p$
C
）A.$1-p$
B.$p+1$
C.$-p+2026$
D.$\frac{20}{21}p$
答案
8.C
