The pupil knows how to translate the word "art" from English to Belarusian. That's true, teacher knows it. In a year, the teacher wants to check if the pupil still remember the translation of the word. So, the teacher gives him a multiple choice quiz to answer this question. There are 5 options to answer, only one is correct. The correct answer was A and the pupil decided to choose A as an answer (anyway he should choose any answer among 5 options).
So, what is the probability the pupil REALLY remembers how to translate "memory"?
My guessing... Let me started, please.
Lets say the event the pupil remembers how to translate the word is R. We have to find P(R) - the probability the pupil still remembers the translation.
Let's A is the event the person chooses A in the quiz.
We have two conditional probabilities:
P (A|not R)=0.2 (he doesn't know the answer)
P (A|R)=1 (if he knows how to translate, he answers A, because that is the correct answer).
We have to find P(R).
Can we or we can't?
I think we can actually add P(A)=P(B)=P(C)=P(D)=P(E)=0.2, if that helps (any of 5 options A,B,C,D,E could be correct, there is no more information about probable answer).