2012 Mock Q40

Hey All,

Looking for some clarification here. I answered C to this problem due to the fact that there is no explicit comment in the text saying that the duration of a bond is ~75% of its maturity. Upon consulting the CFAI text (Vol 5 483-487), I noted that in the blue box the say to use the 75% rule as an assumption only (p. 486 specically mentions using 75% for convience sake) but that this is simply an assumption for the particular problem outlined, not a hard fast rule.

It seems to me that requiring the canidate to make an assumption that is not explicitly stated is a bit unfair. Does anyone know if in other practice problems they have seen the correct answer to the question require the 75% assumption? Should I be using the 75% as a hard fast rule from now on?

Thanks for any help.

This is only for swaps. Fixed rate duration = 75% the maturity, floating = 50% the reset length

Both are just rules of thumb, but I’ve seen both show up a bunch

Ahh, I see. Thanks for the clarification.