登录
1. $(+15)+(+12)= $______
答案
27
2. $(-27)+17= $______
答案
-10
3. $\left( -3\frac{1}{7} \right)+\left( -3\frac{1}{7} \right)= $______
答案
$-6\frac{2}{7}$
4. $-7.25-(+2.75)= $______
答案
-10
解析
$-7.25 - 2.75 = -10$
5. $\frac{1}{2}-\left( -\frac{3}{4} \right)= $______
答案
$\frac{5}{4}$
解析
$\frac{1}{2}-\left(-\frac{3}{4}\right)=\frac{1}{2}+\frac{3}{4}=\frac{2}{4}+\frac{3}{4}=\frac{5}{4}$
6. $\left( -\frac{1}{6} \right)-\frac{1}{3}= $______
答案
$-\frac{1}{2}$
解析
$\left(-\frac{1}{6}\right)-\frac{1}{3}=-\frac{1}{6}-\frac{2}{6}=-\frac{3}{6}=-\frac{1}{2}$
7. $-78+$(______)$=-100$
答案
-22
解析
设括号内的数为$x$，则$-78 + x = -100$，$x = -100 + 78 = -22$
-22
-22
8. $-96+$(______)$=-12$
答案
84
解析
设横线上的数为$x$，则$-96 + x = -12$，解得$x = -12 + 96 = 84$。84
9. $(+35)-$(______)$=-100$
答案
135
解析
设括号内的数为$x$，则$(+35)-x=-100$，移项可得$x=35 - (-100)=35 + 100=135$。135
10. $\left( -\frac{10}{3} \right)+\left( ______ \right)= -\frac{1}{3}$
答案
3
解析
设所求的数为$x$，则$\left(-\frac{10}{3}\right) + x = -\frac{1}{3}$，解得$x = -\frac{1}{3} - \left(-\frac{10}{3}\right) = -\frac{1}{3} + \frac{10}{3} = 3$。
3
3
11. $4.35+(-0.6)-0.25-(+5.4)$
答案
-1.9
解析
$4.35 + (-0.6) - 0.25 - (+5.4)$
$=4.35 - 0.6 - 0.25 - 5.4$
$=(4.35 - 0.25) + (-0.6 - 5.4)$
$=4.1 - 6$
$=-1.9$
$=4.35 - 0.6 - 0.25 - 5.4$
$=(4.35 - 0.25) + (-0.6 - 5.4)$
$=4.1 - 6$
$=-1.9$
12. $4.35-(-0.6)-(-0.25)-(-5.4)$
答案
10.6
解析
$4.35 - (-0.6) - (-0.25) - (-5.4)$
$=4.35 + 0.6 + 0.25 + 5.4$
$=(4.35 + 0.25) + (0.6 + 5.4)$
$=4.6 + 6$
$=10.6$
$=4.35 + 0.6 + 0.25 + 5.4$
$=(4.35 + 0.25) + (0.6 + 5.4)$
$=4.6 + 6$
$=10.6$
13. $(+17)-(-23)-(-13)-32$
答案
21
解析
$(+17)-(-23)-(-13)-32$
$=17 + 23 + 13 - 32$
$=40 + 13 - 32$
$=53 - 32$
$=21$
$=17 + 23 + 13 - 32$
$=40 + 13 - 32$
$=53 - 32$
$=21$
14. $\left| -2\frac{4}{5}-\left( +1\frac{1}{4} \right) \right|-\left| 4\frac{1}{2}-7\frac{1}{5} \right|$
答案
$\frac{27}{20}$
解析
$\left| -2\frac{4}{5}-\left( +1\frac{1}{4} \right) \right|-\left| 4\frac{1}{2}-7\frac{1}{5} \right|$
$=\left| -\frac{14}{5}-\frac{5}{4} \right|-\left| \frac{9}{2}-\frac{36}{5} \right|$
$=\left| -\frac{56}{20}-\frac{25}{20} \right|-\left| \frac{45}{10}-\frac{72}{10} \right|$
$=\left| -\frac{81}{20} \right|-\left| -\frac{27}{10} \right|$
$=\frac{81}{20}-\frac{54}{20}$
$=\frac{27}{20}$
$=\left| -\frac{14}{5}-\frac{5}{4} \right|-\left| \frac{9}{2}-\frac{36}{5} \right|$
$=\left| -\frac{56}{20}-\frac{25}{20} \right|-\left| \frac{45}{10}-\frac{72}{10} \right|$
$=\left| -\frac{81}{20} \right|-\left| -\frac{27}{10} \right|$
$=\frac{81}{20}-\frac{54}{20}$
$=\frac{27}{20}$
15. $\left( -8\frac{3}{7} \right)+(-7.5)+\left( -21\frac{4}{7} \right)+\left( +3\frac{1}{2} \right)$
答案
-34
解析
$\begin{aligned}&\left( -8\frac{3}{7} \right)+\left( -21\frac{4}{7} \right)+(-7.5)+\left( +3\frac{1}{2} \right)\\=&\left[ \left( -8 - \frac{3}{7} \right) + \left( -21 - \frac{4}{7} \right) \right] + \left( -7.5 + 3.5 \right)\\=&\left[ -8 - 21 - \left( \frac{3}{7} + \frac{4}{7} \right) \right] + (-4)\\=&\left( -29 - 1 \right) - 4\\=&-30 - 4\\=&-34\end{aligned}$
16. $\left( -4\frac{1}{3} \right)-\left( -5\frac{1}{3} \right)-(-2.85)-\left( -2\frac{17}{20} \right)$
答案
6.7
解析
$\left( -4\frac{1}{3} \right)-\left( -5\frac{1}{3} \right)-(-2.85)-\left( -2\frac{17}{20} \right)$
$=-4\frac{1}{3}+5\frac{1}{3}+2.85+2\frac{17}{20}$
$=\left( -4\frac{1}{3}+5\frac{1}{3} \right)+\left( 2.85+2\frac{17}{20} \right)$
$=1+\left( 2.85+2.85 \right)$
$=1+5.7$
$=6.7$
$=-4\frac{1}{3}+5\frac{1}{3}+2.85+2\frac{17}{20}$
$=\left( -4\frac{1}{3}+5\frac{1}{3} \right)+\left( 2.85+2\frac{17}{20} \right)$
$=1+\left( 2.85+2.85 \right)$
$=1+5.7$
$=6.7$
