《2025年拔尖特训七年级数学上册人教版》

1. 计算：
(1)28+(-36)+7+(-19)+20.
(2)-101+36+(-12)+(-37)-(-28).
(3)$-5\frac {5}{6}-3\frac {3}{7}+(-2\frac {1}{6})-(-4\frac {3}{7})$.
(4)$-1\frac {2}{3}-2\frac {3}{5}+5-\frac {1}{3}-\frac {2}{5}+4$.

答案： 1.（1）原式=(28+7+20)+(-36-19)=55-55=0.
（2）原式=(-101-12-37)+(36+28)=-150+64=-86.
（3）原式=$(-5\frac {5}{6}-2\frac {1}{6})+(4\frac {3}{7}-3\frac {3}{7})=-8+1=-7$.
（4）原式=$(-1\frac {2}{3}-\frac {1}{3})+(-2\frac {3}{5}-\frac {2}{5})+(5+4)=-2-3+9=4$.

2. 计算：
(1)$(+\frac {1}{4})+(+\frac {1}{8})+19+(-\frac {3}{8})+(-\frac {5}{8})+(-19)$.
(2)$-20.75-3.25+\frac {1}{4}+19\frac {3}{4}$.
(3)$2\frac {1}{2}-0.4+2-2.5+13-7\frac {3}{5}$.
(4)$(-5\frac {1}{3})+4.19+5\frac {3}{8}+(-4\frac {3}{4})+9.81+(-4\frac {2}{3})$.

答案： 2.（1）原式=[19+(-19)]+$\left[(+\frac{1}{4})+(+\frac{1}{8})+(-\frac{3}{8})\right]$$+(-\frac {5}{8})=-\frac {5}{8}$.
（2）原式=$(-20.75+19\frac {3}{4})+(\frac {1}{4}-3.25)=-1-3=-4$.
（3）原式=$(2\frac {1}{2}-2.5)+(-0.4-7\frac {3}{5})+(2+13)=0-8+15=7$.
（4）原式=$(-5\frac {1}{3}-4\frac {2}{3})+(4.19+9.81)+(5\frac {3}{8}-4\frac {3}{4})=-10+14+\frac {5}{8}=4\frac {5}{8}$.

3. 计算：
(1)$-2025\frac {1}{4}-2026\frac {2}{5}+4045\frac {2}{5}-1\frac {1}{2}$.
(2)$-5\frac {5}{6}+(-9\frac {2}{3})+17\frac {3}{4}+(-3\frac {1}{2})$.
(3)$(-4\frac {7}{8})+(+8\frac {1}{4})+(-3\frac {1}{8})$.

答案： 3.（1）原式=$[(-2025)+(-\frac {1}{4})]+[(-2026)+(-\frac {2}{5})]+(4045+\frac {2}{5})+[(-1)+(-\frac {1}{2})]=[(-2025)+(-2026)+4045+(-1)]+$$\left[(-\frac{1}{4})+(-\frac{2}{5})+\frac{2}{5}+(-\frac{1}{2})\right]$$=-7+(-\frac {3}{4})=-7\frac {3}{4}$.
（2）原式=$[(-5)+(-\frac {5}{6})]+[(-9)+(-\frac {2}{3})]+(17+\frac {3}{4})+[(-3)+(-\frac {1}{2})]=[(-5)+(-9)+17+(-3)]+$$\left[(-\frac{5}{6})+(-\frac{2}{3})+\frac{3}{4}+(-\frac{1}{2})\right]$$=0+(-\frac {5}{4})=-\frac {5}{4}$.
（3）原式=$[(-4)+(-\frac {7}{8})]+(8+\frac {1}{4})+[(-3)+(-\frac {1}{8})]=(-4+8-3)+(-\frac {7}{8}+\frac {1}{4}-\frac {1}{8})=1+(-\frac {3}{4})=\frac {1}{4}$.