Independent solution
How to solve this Perpetuity Duration question
Setup
Setup
For a unit perpetuity-immediate, price is the sum of vᵗ and the time-weighted numerator is the sum of tvᵗ.
Model
Model
Dividing the two convergent geometric-series identities gives Macaulay duration 1/d, where d = i/(1 + i).
Compute
Compute
At i = 10%, 1/d = 1.10/0.10 = 11 years.
Answer
Answer
The calculation gives 11 years for perpetuity duration, matching published choice C.