# What does “by what part” mean?

I have a homework problem that is asking me for something. Here's the last line quoted:

If you switch to the ring, by what part will you decrease the electric field magnitude at P?

Okay, so the only problem that I'm facing is that I'm not sure whether this wants a percentage, or a decimal. For example, my answer came out to be 0.11. Would this be asking for 11%, or just the decimal like it is right now?

Thanks, and sorry for such a basic question.

Edit: the whole question reads like the following:

Suppose you design an apparatus in which a uniformly charged disk of radius R is to produce an electric field. The field magnitude is most important along the central perpendicular axis of the disk, at a point P at distance 3.10R from the disk (Fig. 22-52a). Cost analysis suggests that you switch to a ring of the same outer radius R but with inner radius R/3.10 (Fig. 22-52b). Assume that the ring will have the same surface charge density as the original disk. If you switch to the ring, by what part will you decrease the electric field magnitude at P?

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Perhaps you should add the rest of the question, just like that, nothing is obvious. – Patrick Da Silva Mar 31 '12 at 20:13
@PatrickDaSilva: I added it for you. – BigBoy. Mar 31 '12 at 20:14
Personally, I'd ask the instructor, but if this is not an option, I'd just write both. E.g. [..] by 0.11, i.e. 11%. – user2468 Mar 31 '12 at 20:22
@J.D.: How I wish I could do that. Unfortunately, the grading system is computerized, so the answer is either right or wrong, no explanations accepted. – BigBoy. Mar 31 '12 at 20:23
Ops! Good luck then! – user2468 Mar 31 '12 at 20:25