This Exam FM sample reference tests Unit-Payment Loan Amortization Identities. The loan advances a-angle-n and receives total payments n. Since all principal repaid equals the initial loan, total interest is n minus a-angle-n; therefore choice A is true.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
BChoice B equals the interest portion of the first payment, not total interest over the schedule.
CChoice C subtracts first-period interest from total payments and incorrectly labels the result total principal.
DChoice D is one exponent short; principal in payment t is v to the n minus t plus one.
EChoice E confuses the present value of payments with their undiscounted total amount n.
Original practice · fully worked
Original variant: principal component of a specified payment
A loan is amortized by payments of 1 at each period-end for n periods at rate i. With v equal to 1/(1+i), which expression gives the principal repaid in payment t?
A v raised to n−t
B v raised to n−t+1
C i times a-angle-(n−t+1)
D 1 minus v raised to n−t+1
E a-angle-(n−t)
Variant answer in brief
Immediately before payment t, the balance is a-angle-(n−t+1). Subtracting its interest portion from 1 gives principal v to the n−t+1, choice B.
Setup
Setup
There are n minus t plus one payments remaining immediately before payment t.
Bt−1=an−t+1∣i
Model
Model
The interest portion of payment t is i times that balance.
It=iBt−1
Compute
Compute
Principal is payment minus interest; use one minus i a-angle-m equals v to the m.
The 2210-page Financial Mathematics Proof Manual reorganizes 461 verified Exam FM solutions by syllabus skill and adds formula proofs, error patterns, and original worked practice.