Answer:17.3 years
Explanation:
We would apply the formula for exponential growth which is expressed as
A = P(1 + r)^ t
Where
A represents the population after t years.
t represents the number of years.
P represents the initial population.
r represents rate of growth.
From the information given,
A = 42800
P = 20000
r = 4.5% = 4.5/100 = 0.045
Therefore
42800 = 20000(1 + 0.045)^t
42800/20000 = (1.045)^t
2.14 = (1.045)^t
Taking log of both sides to base 10
Log 2.14 = log1.045^t = tlog1.045
0.3304 = t × 0.0191
0.3304 = 0.0191t
t = 0.3304/0.0191
t = 17.3 years