Answer: 8.5 years
Explanation:
Hi, to answer this question we have to apply an exponential growth function:
A = P (1 + r) t
Where:
p = original population
r = growing rate (decimal form) =18/100 = 0.18
t= years
A = population after t years
Replacing with the values given:
192,000 = 47,000 (1+ 0.18)^t
Solving for t:
192,000/47,000 = 1.18^t
4.08 =1.18^t
ln 4.08 = ln 1.18^t
ln 4.08 =t (ln 1.18)
ln 4.08 / ln 1.18 =t
8.5 years = t
Feel free to ask for more if needed or if you did not understand something.