This Exam FM sample reference tests Annuities. Equating the 20-year 1,000 annuity to a perpetuity paying 600 for ten years then 1,200 reduces to a quadratic in the ten-year discount factor. The valid root is 0.4, giving rate 9.5958% and common value 8753.81, choice B.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
AChoice A (8700) does not satisfy the equality between the finite 20-year annuity and the decomposed stepped perpetuity; no distinct standard one-step error is identifiable.
CChoice C (8800) does not satisfy the equality between the finite 20-year annuity and the decomposed stepped perpetuity; no distinct standard one-step error is identifiable.
DChoice D (8850) does not satisfy the equality between the finite 20-year annuity and the decomposed stepped perpetuity; no distinct standard one-step error is identifiable.
EChoice E (8900) does not satisfy the equality between the finite 20-year annuity and the decomposed stepped perpetuity; no distinct standard one-step error is identifiable.
Original practice · fully worked
Original variant: later perpetuity payment required to match a finite annuity
At a 6% annual yield, a 15-year annuity pays 1,000 each year. A second stream pays 500 in each of years 1 through 5 and then pays Y annually forever beginning in year 6. Calculate Y so the two streams have equal present value.
A 610.72
B 641.25
C 671.79
D 702.33
E 732.86
Variant answer in brief
The 15-year annuity value minus the first five 500 payments is the time-0 value of the deferred Y perpetuity. Moving that residual to time 5 and multiplying by 6% gives Y = 610.72, choice A.
Setup
Setup
Value the finite 15-year annuity and the first five payments of the stepped stream.
PA=1000a15∣0.06
P1:5=500a5∣0.06
Model
Model
The residual present value is a perpetuity-immediate valued at time 5 and discounted back five years.
PA−P1:5=0.06Y(1.06)−5
Compute
Compute
Solving gives later annual payment 610.72.
Y=0.06(1.06)5(PA−P1:5)=610.71801188
Answer
Answer
The later perpetuity payment is 610.72, selecting choice A.
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