4. 计算:
(1) $45×(-25)×\frac{7}{8}×(-\frac{11}{15})÷\frac{1}{4}×(-1\frac{1}{7})$。
(2) $2×(-\frac{4}{9})+1.53×\frac{4}{9}-9.47×(-\frac{4}{9})-(\frac{7}{9}-\frac{5}{6}+\frac{1}{4}-\frac{1}{18})×72$。
(1) $45×(-25)×\frac{7}{8}×(-\frac{11}{15})÷\frac{1}{4}×(-1\frac{1}{7})$。
(2) $2×(-\frac{4}{9})+1.53×\frac{4}{9}-9.47×(-\frac{4}{9})-(\frac{7}{9}-\frac{5}{6}+\frac{1}{4}-\frac{1}{18})×72$。
答案
(1) 原式$=-(45×\frac{11}{15})×(25×4)×(\frac{7}{8}×\frac{8}{7})=-33×100×1=-3300$.
(2) 原式$=(2-1.53-9.47)×(-\frac{4}{9})-(\frac{7}{9}×72-\frac{5}{6}×72+\frac{1}{4}×72-\frac{1}{18}×72)=(-9)×(-\frac{4}{9})-(56-60+18-4)=4-10=-6$.
(2) 原式$=(2-1.53-9.47)×(-\frac{4}{9})-(\frac{7}{9}×72-\frac{5}{6}×72+\frac{1}{4}×72-\frac{1}{18}×72)=(-9)×(-\frac{4}{9})-(56-60+18-4)=4-10=-6$.
5. 计算:
(1) $(-1 \frac{1}{2})+(-57 \frac{13}{20})-(-1 \frac{1}{2})+42 \frac{7}{20}.$
(2) $(-199 \frac{37}{38}) × 76.$
(1) $(-1 \frac{1}{2})+(-57 \frac{13}{20})-(-1 \frac{1}{2})+42 \frac{7}{20}.$
(2) $(-199 \frac{37}{38}) × 76.$
答案
(1) 原式$=-1\ \frac{1}{2}-57\ \frac{13}{20}+1\ \frac{1}{2}+42\ \frac{7}{20}=-1-\frac{1}{2}-57-\frac{13}{20}+1+\frac{1}{2}+42+\frac{7}{20}=(-1-57+1+42)+(-\frac{1}{2}+\frac{1}{2})+(-\frac{13}{20}+\frac{7}{20})=-15-\frac{3}{10}=-15\ \frac{3}{10}$.
(2) 原式$=(-200+\frac{1}{38})×76=-200×76+\frac{1}{38}×76=-15200+2=-15198$.
(2) 原式$=(-200+\frac{1}{38})×76=-200×76+\frac{1}{38}×76=-15200+2=-15198$.
6. 计算:$(-\dfrac{1}{24})÷(\dfrac{2}{3}-\dfrac{1}{12}+\dfrac{1}{6}-\dfrac{1}{4}).$
答案
原式的倒数为$(\frac{2}{3}-\frac{1}{12}+\frac{1}{6}-\frac{1}{4})÷(-\frac{1}{24})=(\frac{2}{3}-\frac{1}{12}+\frac{1}{6}-\frac{1}{4})×(-24)=\frac{2}{3}×(-24)-\frac{1}{12}×(-24)+\frac{1}{6}×(-24)-\frac{1}{4}×(-24)=-16+2-4+6=-12$. 所以原式$=-\frac{1}{12}$.
7. 计算:
(1) $1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + 9 - 10 - 11 + \dots + 2021 - 2022 - 2023$。
(2) $1 - 3 × 2 + 5 + 7 - 9 × 2 + 11 + 13 - 15 × 2 + 17 + \dots + 2011 - 2013 × 2 + 2015 + 2017$。
(1) $1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + 9 - 10 - 11 + \dots + 2021 - 2022 - 2023$。
(2) $1 - 3 × 2 + 5 + 7 - 9 × 2 + 11 + 13 - 15 × 2 + 17 + \dots + 2011 - 2013 × 2 + 2015 + 2017$。
答案
(1) 原式$=(1-2-3+4)+(5-6-7+8)+\dots+(2017-2018-2019+2020)+(2021-2022-2023)=0+0+\dots+0-2024=-2024$.
(2) 原式$=(1-3×2+5)+(7-9×2+11)+(13-15×2+17)+\dots+(2011-2013×2+2015)+2017=0+0+…+0+2017=2017$.
(2) 原式$=(1-3×2+5)+(7-9×2+11)+(13-15×2+17)+\dots+(2011-2013×2+2015)+2017=0+0+…+0+2017=2017$.
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