This Exam FM sample reference tests Annuities and Perpetuities. The increasing stream begins immediately, so shifting the standard increasing annuity one period earlier gives value (1.05)² divided by 0.05² = 441, choice D.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
AChoice A is inconsistent with the generating-function value of the increasing perpetuity-due; no distinct standard single-step error producing it is identifiable.
BChoice B is inconsistent with the generating-function value of the increasing perpetuity-due; no distinct standard single-step error producing it is identifiable.
CChoice C is inconsistent with the generating-function value of the increasing perpetuity-due; no distinct standard single-step error producing it is identifiable.
EChoice E is inconsistent with the generating-function value of the increasing perpetuity-due; no distinct standard single-step error producing it is identifiable.
Original practice · fully worked
Original variant: interest rate inferred from an increasing perpetuity
A perpetuity-immediate pays 1 after one year, 2 after two years, and continues increasing by one each year. Its present value is 110. Determine the annual effective interest rate.
A 8.00%
B 9.00%
C 10.00%
D 11.00%
E 12.00%
Variant answer in brief
The increasing perpetuity-immediate value is one plus i divided by i squared; setting it to 110 gives i = 10%, choice C.
Setup
Setup
Use the standard value of an increasing perpetuity whose first payment is in year one.
110=i21+i
Model
Model
Rearrange the value equation into a quadratic in the positive annual rate.
110i2−i−1=0
Compute
Compute
The positive root is 0.10; the other root is economically inadmissible.
i=2201+441=0.10
Answer
Answer
The annual effective rate is 10.00%, corresponding to choice C.
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