Original practice · fully worked
Original variant: original principal recovered from a later balance
A loan charges 6% annual effective interest. After five end-of-year payments of 600, its balance immediately after payment 5 is 4,200. Calculate the original loan principal.
- A
5,665.90 - B
5,949.20 - C
6,232.49 - D
6,515.79 - E
6,799.08
Answer and calculation
At year 5, accumulated principal equals the 4,200 remaining balance plus the accumulated value of five payments. Discounting that total gives original principal 5,665.90, choice A.
Setup
Setup
Write the retrospective balance at time 5 with the original principal as the unknown.
4200=L(1.06)5−600s5∣0.06 Model
Model
Move the accumulated payments to the balance side and discount five years.
L=(1.06)54200+600s5∣0.06 Compute
Compute
The resulting original principal is 5665.90.
L=5665.902597 Answer
Answer
The original loan was 5,665.90, which is choice A.
L≈5665.90(A) Calculator reproduction
BA II Plus keystrokes
- 2ND · CLR TVM · 5 · N · 6 · I/Y · 600 · +/- · PMT · 4200 · +/- · FV · CPT · PVPV = 5665.90The payment and ending balance have the same sign, opposite the initial loan.