This Exam FM sample reference tests Duration and Convexity. Macaulay duration 11 at yield 10% corresponds to modified duration 10; a 0.25-point yield increase therefore changes price by approximately −10(0.0025) = −2.50%, choice C.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
AChoice A is inconsistent with the modified-duration linear price approximation; no distinct standard single-step error producing it is identifiable.
BChoice B is inconsistent with the modified-duration linear price approximation; no distinct standard single-step error producing it is identifiable.
DChoice D is inconsistent with the modified-duration linear price approximation; no distinct standard single-step error producing it is identifiable.
EChoice E is inconsistent with the modified-duration linear price approximation; no distinct standard single-step error producing it is identifiable.
Original practice · fully worked
Original variant: infer modified duration from an observed price move
A food-bank bond is priced at 5,000. After a 20-basis-point increase in yield, its first-order estimated price change is a decrease of 75. Determine the modified duration used in the estimate.
A 5.0
B 6.0
C 7.5
D 8.5
E 10.0
Variant answer in brief
A 75 decline is 1.5% of price; dividing by the 0.002 yield increase gives modified duration 7.5, choice C.
Setup
Setup
Convert the dollar decline to a proportional price change and 20 basis points to 0.002.
PΔP=5000−75=−0.015
Model
Model
The first-order relation equates the magnitude of that proportional decline to duration times yield change.
PΔP≈−DmodΔi
Compute
Compute
Dividing 0.015 by 0.002 gives 7.5.
Dmod=0.0020.015=7.5
Answer
Answer
The inferred modified duration is 7.5, corresponding to choice C.
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