Sometimes, it's a judgement call, but I'll try and give some guidelines:
If it's a problem solving style question (which yours doesn't seem to be), the problem statement should be the same. That is, when the problem is distilled down to a single sentence for the two questions, and those sentences are identical or nearly identical, then one question is probably a dupe of the other. Something to realize with this is that we're concerned with the symptoms, not the cause, so the same problem can have two (or more) different solutions if there are two (or more) root causes, but it's still the same problem, and therefore a dupe.
It's a similar thing for fact finding questions. Two questions have to be seeking the same piece of information. Sometimes, this is non-obvious to the second person asking. They don't realize they're asking the same question.
But two questions can have the same answer and not be dupes. Two problems can have the same solution but still be vastly different problems.
So in your case, you're looking for two different facts that just happen to be related. Having said that, I wouldn't ask the question now unless you intend to self answer immediately.