approximation by semiinfinite slopes

例句：

1. 1. Thedistance between the two cities is approximately500 kilometers.
   两座城市之间的距离大约是500公里。
2. 2. Theteacher estimated the final scoreto be around 80points.
   老师估计最终分数在80分左右。
3. 3. The project's budgetwas an approximation of $1 million.
   该项目的预算约为100万美元。