Question

两道英文数学题，求解！急用，O(∩_∩)O谢谢！！（不用翻译）

1. The enrollment at Hardknocks University is increasing exponentially. There were
5000 students enrolled when the university opened. Three years later, the enrollment
had reached 8000 students. Assuming this growth rate is continous, what will be the
enrollment after 6 years?

2. How long will it take for the enrollment at Hardknocks University to triple?

Answer 1

1. 设growth rate 为x%
则5000*(1+x%)^3=8000
(1+x%)^3=8/5
6年后的enrollment=5000*(1+x%)^6=5000*(8/5)^2=12800
2. 设x年后the enrollment at Hardknocks University to triple
5000*(1+x%)^x=15000
(8/5)^(x/3)=3
x≈7
即7年后，登记入学的人数达3倍。

Answer 2

8000-5000=3000 3000/3=1000 1000/5000=0.2三年内的入学率为0.2
设6年后学生人数增长为x人
（x-5000)X0.2+5000即求出了第一题