Original practice · fully worked
Original variant: principal supported by declining payments
A borrower promises eight annual payments, beginning with 3,000 at the end of year 1. Each later payment is 3% smaller than the preceding one. At a 5% annual effective loan rate, determine the original principal advanced.
- A
15,984.22 - B
16,705.90 - C
17,190.41 - D
17,607.44 - E
18,442.08
Answer and calculation
Discounting the eight payments 3000 times 0.97 to successive powers at 5% gives an original principal of 17607.44, choice D.
Setup
Setup
Payment k equals 3000 times 0.97 to the k minus one.
Ck=3,000(0.97)k−1 Model
Model
The principal is the present value of all eight promised payments.
L=k=1∑81.05k3,000(0.97)k−1 Compute
Compute
Evaluate the finite geometric series.
L=17,607.4367 Answer
Answer
The loan principal is 17607.44, choice D.
L=17,607.44(D)