✔ 最佳答案
Let x% be the annual growth rate.
Let a be the original population.
The population in 30 years.
a (1 + x%)^30 = 3 a
(1 + x%)^30 = 3
log[(1 + x%)^30] = log(3)
30 log(1 + x%) = log(3)
log(1 + x%) = (1/30) log(3)
1 + x% = 10^[(1/30) log(3)]
x% = 10^[(1/30) log(3)] - 1
x% = 0.0373
x = 3.73
The annual growth rate = 3.73%