Answer:
Blume's formula combines the geometric and arithmetic means of an asset to be able to predict its returns in a given period.
The formula is;
= Geometric Mean*(T-1)/(N-1) + Arithmatic Mean *(N-T)/(N-1)
Where;
T = Period in question
N = Total period
10 years
= 8.3%*(10-1)/(90-1) + 10.3%*(90-10)/(90-1)
= 10.1 %
25 years
= 8.3%*(25-1)/(90-1) + 10.3%*(90-25)/(90-1)
= 9.76%
30 years
= 8.3%*(30-1)/(90-1) + 10.3%*(90-30)/(90-1)
= 9.65%