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
Answer and calculation
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.
Dmod=7.5(C)