Independent solution

How to solve this Equivalent Growing Annuities question

Setup

Setup

Value the first annuity as a finite growing annuity-immediate.

PVX=t=1202,500(1.05)t11.04t=52,732.6093PV_X=\sum_{t=1}^{20}\frac{2{,}500(1.05)^{t-1}}{1.04^t}=52{,}732.6093

Model

Model

For the second annuity, each 4% payment increase exactly cancels one year's 4% discount.

k(1.04)t(1.04)t=k,t=0,,29\frac{k(1.04)^t}{(1.04)^t}=k,\qquad t=0,\ldots,29

Compute

Compute

Its thirty discounted payments therefore have value 30k.

30k=52,732.609330k=52{,}732.6093
k=1,757.7536k=1{,}757.7536

Answer

Answer

The initial payment is approximately 1758, choice A.

k1,758(A)\boxed{k\approx1{,}758\quad\text{(A)}}