I've run into one of those cases again where both the definite and indefinite article seem to work. And that makes me very confused as it makes it harder for me to grasp the concept of the articles. Here are some sample sentences that I found on the internet.
At the outset of the interview students were told that if they did not
know an answer they could say "pass" and move on to the next
question.It is always a good idea to go over the test to make sure that you
answered every question. If you do not know the answer, guess.
You may get the right answer or partial credit.It can be a reasoning exercise in which the student has to figure out
an answer on her or his own.The teacher-librarian serves as a guide to help students figure out
the answer on their own.
Are the articles in these sentences interchangeable?
So if you are not talking about any specific answer (you don't know what an answer can be), do you use a or the, or it doesn't matter?
Again, the answer seems to be more common, according to my research, so is it more idiomatic?
Best Answer
If a particular question could have multiple answers, you would use an answer. If a particular question has one answer, you would use the answer.
However, if you have multiple questions (as in your interview example), you have multiple answers (not necessarily per question - each may have exactly one answer or many answers). In this case you would use an answer, since there is more than one answer in the interview (but not necessarily more than one per question).
To address your examples:
There are multiple questions in an interview. It's possible they will each have only one correct answer; even in that case there are many answers throughout the interview.
This one, I expect, is contributing to your confusion. Each question on the test has a single answer, but the test has many. The first sentence talks about the test as a whole, where it can be understood that the second and third sentence talk about a particular question (without making the transition very obvious, other than using "the answer" and "the right answer").
It's a reasonable expectation that a reasoning exercise may have multiple correct answers (or no correct answer at all), and that each student will likely come up with something different.
This likely refers to the general case of a student having a question. The student wants to find the answer to the question (or possibly an answer). For the general case of an unknown/unspecified question, the answer is usually used (at least I would, and that seems to be what I've seen), although an answer would also be correct.