This Exam FM sample reference tests Interest Rate Measures. Writing the present-value equality as a quadratic in v produces discount factors 0.970874 and 0.952381, corresponding to 3% and 5% annual rates. Their absolute difference is 2%, so choice B is correct.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
AChoice A (1.8%) does not satisfy both positive roots of the present-value quadratic in the one-year discount factor; no distinct standard one-step error is identifiable.
CChoice C (3.0%) does not satisfy both positive roots of the present-value quadratic in the one-year discount factor; no distinct standard one-step error is identifiable.
DChoice D (4.0%) does not satisfy both positive roots of the present-value quadratic in the one-year discount factor; no distinct standard one-step error is identifiable.
EChoice E (5.0%) does not satisfy both positive roots of the present-value quadratic in the one-year discount factor; no distinct standard one-step error is identifiable.
Original practice · fully worked
Original variant: sum of two yields satisfying one nonconventional value equation
The present value of 8,550 now plus 10,000 at year 2 equals the present value of 18,500 at year 1 at two positive annual effective rates. Calculate the sum of those two rates.
A 15.56%
B 16.37%
C 17.19%
D 18.01%
E 18.83%
Variant answer in brief
The value equation factors into discount roots 0.95 and 0.90. These correspond to rates 5.26% and 11.11%, whose sum is 16.37%, choice B.
Setup
Setup
Write the equality as a quadratic in the annual discount factor.
8550+10000v2=18500v
Model
Model
Factor the quadratic to obtain both positive discount roots.
10000(v−0.95)(v−0.90)=0
Compute
Compute
The corresponding rates are 5.263158% and 11.111111%, summing to 16.374269%.
i1=1/0.95−1
i2=1/0.90−1
Answer
Answer
The sum of the two rates is 16.37%, selecting choice B.
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