If you knew that, you’ve passed what used to be one of Google’s mind-scrambling job-interview questions. (the source)
I can’t understand what conditional it is and wether it is a conditional at all. The first clause is in Past, but the second is in Present Perfect. And there is no “would” at all, but definitely it is an unreal conditional.
This is an elaboration on other answers (particularly StoneyB’s) but is too long to fit as a comment.
Part of the difficulty here may be because in most cases if + past simple clauses fulfil one of two functions:
to introduce a hypothesis about a seemingly unlikely future event
to introduce a counterfactual.
This is the archetypical Conditional 2. Examples are:
If I won a lot of money, I would retire immediately (but I don’t expect
to win a lot of money).
If I knew the answer, I would tell you (but I don’t know the answer).
In both cases the main clause usually contains would or could.
However, in the sentence: If you knew that, you’ve passed … . we are dealing with a past event which may or may not be true. Either you knew it or you didn’t. However, if you did know, then … . And what comes in the main clause after the then can be in any appropriate tense to convey your meaning:
If you knew the answer, you are one of the few that did.
If you knew the answer, you passed the test.
If you knew the answer, you’ve passed the test.
If you knew the answer, you will have passed the test.
If you knew the answer, you can feel proud of yourself.
If you knew the answer, you might get the job.