Answer:
19. 8 years
Step-by-step explanation:
Using the exponential growth function :
A = Pe^rt
A = final amount or growth unit
P = initial or present growth unit
Rate, r = growth rate
80 = 20e^0.07t
80/20 = e^0.07t
4 = e^0.07t
Take In of both sides
In(4) = 0.07t
1.3862943 = 0.07t
t = 19.804205
t = 19. 8 years
