This Exam FM sample reference tests Loan Amortization. Equating the original 15-payment value to the revised ten-year stream gives 50a₁₅ = 50a₁₀ + 30v⁵a₅; accumulating to year 10 produces the expression in choice C.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
AThis leaves the equation at inconsistent dates and omits the required accumulation of the original stream.
BThe first term lacks the five-year timing adjustment created when valuing at year ten.
DThis discounts the extra-payment block twice.
EThis accumulates the extra payments from the wrong endpoint and shifts their block.
Original practice · fully worked
Original variant: extra payments needed for an earlier payoff
A twelve-year loan at 5% has annual payments of 100. The borrower instead pays 100 in years 1–3 and 100+X in years 4–8, fully repaying at year 8. Determine X.
A 50.00
B 58.00
C 64.17
D 70.00
E 80.00
Variant answer in brief
Equating the original 12-year value to the revised eight-year stream gives X = 64.17, choice C.
Setup
Setup
Keep the original loan value fixed and compare the two complete repayment streams at the loan date.
100a12∣0.05=100a8∣0.05+Xv3a5∣0.05
Model
Model
The extra amount occurs only in years four through eight, a five-payment annuity deferred three years.
886.3252−646.3216=X(3.740304)
Compute
Compute
The value gap between the original and shortened base streams divided by that deferred factor is 64.1728.
X=64.1728
Answer
Answer
Each of the last five payments must increase by 64.17, choice C.
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.