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1. $-5+7-8+1+17= $______
答案
12
解析
$-5+7-8+1+17$
$=(-5-8)+(7+1+17)$
$=-13+25$
$=12$
$=(-5-8)+(7+1+17)$
$=-13+25$
$=12$
2. $318-139-518= $______
答案
-339
解析
318 - 139 - 518 = 318 - 518 - 139 = -200 - 139 = -339
3. $-5.3+1.6+2.3-3.6= $______
答案
-5
解析
$-5.3 + 2.3 + 1.6 - 3.6$
$=(-5.3 + 2.3) + (1.6 - 3.6)$
$=-3 + (-2)$
$=-5$
$=(-5.3 + 2.3) + (1.6 - 3.6)$
$=-3 + (-2)$
$=-5$
4. $(-138)+(-15\frac {8}{11})+138= $______
答案
$-15\frac{8}{11}$
解析
$(-138)+(-15\frac{8}{11})+138$
$=(-138)+138+(-15\frac{8}{11})$
$=0+(-15\frac{8}{11})$
$=-15\frac{8}{11}$
$=(-138)+138+(-15\frac{8}{11})$
$=0+(-15\frac{8}{11})$
$=-15\frac{8}{11}$
5. $-8×(-9)×(-1.125)= $_____
答案
-81
解析
$-8×(-9)×(-1.125)$
$=-8×(-9)×\left(-\dfrac{9}{8}\right)$
$=(-8)×\left(-\dfrac{9}{8}\right)×(-9)$
$=9×(-9)$
$=-81$
$=-8×(-9)×\left(-\dfrac{9}{8}\right)$
$=(-8)×\left(-\dfrac{9}{8}\right)×(-9)$
$=9×(-9)$
$=-81$
6. $-15\frac {1}{10}+\frac {1}{11}= $______
答案
$-15\frac{1}{110}$
解析
$-15\frac{1}{10}+\frac{1}{11}=-15-\frac{1}{10}+\frac{1}{11}=-15+\left(-\frac{11}{110}+\frac{10}{110}\right)=-15-\frac{1}{110}=-15\frac{1}{110}$
7. $(\frac {3}{5}-\frac {8}{9}-1)×45= $______
答案
-58
解析
$\frac{3}{5} × 45 - \frac{8}{9} × 45 - 1 × 45$
$=27 - 40 - 45$
$=-58$
-58
$=27 - 40 - 45$
$=-58$
-58
8. $\frac {7}{15}×(-12)+(-\frac {8}{15})×12= $______
答案
-12
解析
$\begin{aligned}&\frac{7}{15} × (-12) + \left(-\frac{8}{15}\right) × 12\\=&-\frac{7}{15} × 12 - \frac{8}{15} × 12\\=&12 × \left(-\frac{7}{15} - \frac{8}{15}\right)\\=&12 × \left(-\frac{15}{15}\right)\\=&12 × (-1)\\=&-12\end{aligned}$
-12
-12
9. $0.25÷(-3\frac {2}{13})÷(+\frac {1}{4})$
答案
$-\frac{13}{41}$
解析
$0.25÷(-3\frac{2}{13})÷(+\frac{1}{4})$
$=\frac{1}{4}÷(-\frac{41}{13})÷\frac{1}{4}$
$=\frac{1}{4}×(-\frac{13}{41})×4$
$=\frac{1}{4}×4×(-\frac{13}{41})$
$=1×(-\frac{13}{41})$
$=-\frac{13}{41}$
$=\frac{1}{4}÷(-\frac{41}{13})÷\frac{1}{4}$
$=\frac{1}{4}×(-\frac{13}{41})×4$
$=\frac{1}{4}×4×(-\frac{13}{41})$
$=1×(-\frac{13}{41})$
$=-\frac{13}{41}$
10. $-2.17+(-2\frac {5}{9})-(+7.83)+(-1\frac {4}{9})$
答案
-14
解析
$-2.17+(-2\frac{5}{9})-(+7.83)+(-1\frac{4}{9})$
$=-2.17-2\frac{5}{9}-7.83-1\frac{4}{9}$
$=(-2.17-7.83)+(-2\frac{5}{9}-1\frac{4}{9})$
$=-10+(-4)$
$=-14$
$=-2.17-2\frac{5}{9}-7.83-1\frac{4}{9}$
$=(-2.17-7.83)+(-2\frac{5}{9}-1\frac{4}{9})$
$=-10+(-4)$
$=-14$
11. $-567\frac {1}{7}+566\frac {1}{8}$
答案
$-1\frac{1}{56}$
解析
$-567\frac{1}{7} + 566\frac{1}{8}$
$=-(567 + \frac{1}{7}) + (566 + \frac{1}{8})$
$=-567 - \frac{1}{7} + 566 + \frac{1}{8}$
$=(-567 + 566) + (-\frac{1}{7} + \frac{1}{8})$
$=-1 + (-\frac{8}{56} + \frac{7}{56})$
$=-1 - \frac{1}{56}$
$=-1\frac{1}{56}$
$=-(567 + \frac{1}{7}) + (566 + \frac{1}{8})$
$=-567 - \frac{1}{7} + 566 + \frac{1}{8}$
$=(-567 + 566) + (-\frac{1}{7} + \frac{1}{8})$
$=-1 + (-\frac{8}{56} + \frac{7}{56})$
$=-1 - \frac{1}{56}$
$=-1\frac{1}{56}$
12. $-999\frac {1}{6}×6$
答案
-5995
解析
$-999\frac{1}{6} × 6$
$=-\left(1000 - \frac{5}{6}\right) × 6$
$=-\left(1000 × 6 - \frac{5}{6} × 6\right)$
$=-(6000 - 5)$
$=-5995$
$=-\left(1000 - \frac{5}{6}\right) × 6$
$=-\left(1000 × 6 - \frac{5}{6} × 6\right)$
$=-(6000 - 5)$
$=-5995$
13. $(-3)×(-\frac {1}{4})+0.25×24.5+(-3\frac {1}{2})×25\%$
答案
6
解析
$(-3) × (-\frac{1}{4}) + 0.25 × 24.5 + (-3\frac{1}{2}) × 25\%$
$=(-3) × (-\frac{1}{4}) + \frac{1}{4} × 24.5 + (-3.5) × \frac{1}{4}$
$=\frac{1}{4} × (3 + 24.5 - 3.5)$
$=\frac{1}{4} × 24$
$=6$
$=(-3) × (-\frac{1}{4}) + \frac{1}{4} × 24.5 + (-3.5) × \frac{1}{4}$
$=\frac{1}{4} × (3 + 24.5 - 3.5)$
$=\frac{1}{4} × 24$
$=6$
14. $15×998+36×(\frac {3}{4}+\frac {5}{6}-\frac {8}{9})-(-15)×(-999)$
答案
10
解析
$15×998+36×\left(\frac{3}{4}+\frac{5}{6}-\frac{8}{9}\right)-(-15)×(-999)$
$=15×998-15×999+36×\frac{3}{4}+36×\frac{5}{6}-36×\frac{8}{9}$
$=15×(998 - 999)+27 + 30 - 32$
$=15×(-1)+25$
$=-15 + 25$
$=10$
$=15×998-15×999+36×\frac{3}{4}+36×\frac{5}{6}-36×\frac{8}{9}$
$=15×(998 - 999)+27 + 30 - 32$
$=15×(-1)+25$
$=-15 + 25$
$=10$
