Answer:
B) It decreases 22% per year.
Step-by-step explanation:
We are given that The value, v(.r), of his portfolio can be modeled with the function : [tex]y(x) = 30,000(0.78)^x[/tex]
Where x is the number of years since he made his investment.
Formula :[tex]P(1-r)^t=A[/tex]
Where P = Principal
r = rate of decrease
t = time
A = Amount after t years
So, On comparing
P = 30000
t=x
A=y(x)
[tex]1-r=0.78[/tex]
[tex]\Rightarrow 1-0.78=r[/tex]
[tex]\Rightarrow 0.22=r[/tex]
So, r = 0.22
r=22%
So, Rate of decrease is 22%
So, Option B is true,
It decreases 22% per year.