Independent solution

How to solve this Annuities and Perpetuities question

Setup

Setup

Keep deposited principal separate from the annual interest transferred for reinvestment.

1260=5(200)+200ik=15k(1.06)5k1260=5(200)+200i\sum_{k=1}^{5}k(1.06)^{5-k}

Model

Model

At year k, interest is based on k deposits and then grows at 6% for the remaining years.

1260=1000+200i(16.2553)1260=1000+200i(16.2553)

Compute

Compute

The accumulated transfer factor is 16.2553, making the source interest rate 8%.

i=2603251.06=0.08i=\frac{260}{3251.06}=0.08

Answer

Answer

The deposits earn 8.00% before transfer, corresponding to choice A.

i=8.00%(A)\boxed{i=8.00\%\quad\text{(A)}}