Original practice · fully worked
Original variant: growth-transition date inferred from a perpetuity price
A perpetuity pays 1 at year 1. Payments initially grow 3% annually; after N early payments, all later payments grow 6% annually. At a 10% yield, the price is 22.5222. Determine N.
- A
3 payments - B
4 payments - C
5 payments - D
6 payments - E
7 payments
Answer and calculation
Testing the finite early-growth block together with the later 6%-growth tail shows the quoted price is produced by N = 4 early payments, choice B.
Setup
Setup
For a candidate N, value the first N payments under 3% growth.
PV1(N)=t=1∑N(1.10)t(1.03)t−1 Model
Model
At time N, append the perpetuity tail beginning with the next 3%-grown payment and then growing 6%.
PV2(N)=0.10−0.06(1.03)N(1.10)−N Compute
Compute
The sum matches the quoted price at N = 4.
PV1(4)+PV2(4)=22.5221892289 Answer
Answer
There are 4 early-growth payments, selecting choice B.
N=4(B)