This Exam FM sample reference tests Duration and Convexity. The discounted liability cash flows total 66.57, and their time-weighted present values total 226.45. Their ratio is 3.40 years, so choice C is correct.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
AChoice A (3.1 years) does not satisfy the ratio of time-weighted discounted liabilities to their total present value; no distinct standard one-step error is identifiable.
BChoice B (3.2 years) does not satisfy the ratio of time-weighted discounted liabilities to their total present value; no distinct standard one-step error is identifiable.
DChoice D (3.5 years) does not satisfy the ratio of time-weighted discounted liabilities to their total present value; no distinct standard one-step error is identifiable.
EChoice E (3.6 years) does not satisfy the ratio of time-weighted discounted liabilities to their total present value; no distinct standard one-step error is identifiable.
Original practice · fully worked
Original variant: final liability amount implied by a target duration
A liability pays 100 at year 1, 200 at year 3, and X at year 5. Values are discounted at 5% annually. Determine X if the liability's Macaulay duration must equal 3.5 years.
A 220.87
B 234.67
C 248.48
D 262.28
E 276.08
Variant answer in brief
Setting the time-weighted present value equal to 3.5 times total present value and isolating the year-5 amount gives X = 276.08, choice E.
Setup
Setup
Write the present-value and duration-numerator contributions of the three liabilities.
PV=100v+200v3+Xv5
N=100v+600v3+5Xv5
Model
Model
Impose the target duration by setting the numerator equal to 3.5 times present value.
100v+600v3+5Xv5=3.5(100v+200v3+Xv5)
Compute
Compute
At 5%, solving the resulting linear equation gives X = 276.08.
X=276.08437500
Answer
Answer
The final liability must be 276.08, which is choice E.
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