Independent solution

How to solve this Portfolio Duration under a Common Yield question

Setup

Setup

Because the coupon bond sells at par, its annual effective yield equals its 6% coupon rate.

i=0.06i=0.06

Model

Model

Compute Bond A's price-weighted timing at this yield.

DA=t=19t(60)vt+10(1,060)v101,000=7.8016923D_A=\frac{\sum_{t=1}^{9}t(60)v^t+10(1{,}060)v^{10}}{1{,}000}=7.8016923

Compute

Compute

Price the two zeroes and use their maturities as durations.

PB=1,000v5=747.2582P_B=1{,}000v^5=747.2582
PC=1,000v10=558.3948P_C=1{,}000v^{10}=558.3948

Answer

Answer

Market-value weighting gives 7.4261 years, choice B.

DP=1,000(7.8016923)+747.2582(5)+558.3948(10)1,000+747.2582+558.3948=7.426066D_P=\frac{1{,}000(7.8016923)+747.2582(5)+558.3948(10)}{1{,}000+747.2582+558.3948}=7.426066
DP7.43(B)\boxed{D_P\approx7.43\quad\text{(B)}}