Thread: Independent Events Question

Hello everyone,

I am having a bit of trouble with finding the answer to this question.
Students A, B, C each independently on a test. The probability of A getting the right answer is 0.9, for B it is 0.7 and for C it is 0.4.

If two of them get the right answer, what is the probability that C got their question wrong.

My logic behind this was finding AB(Not C) = 0.9*0.7*0.6, but apparently this is wrong. The correct answer was 0.7354

Any insight would be much appreciated. THanks!

Originally Posted by KelvinScale

Hello everyone,

I am having a bit of trouble with finding the answer to this question.
Students A, B, C each independently on a test. The probability of A getting the right answer is 0.9, for B it is 0.7 and for C it is 0.4.

If two of them get the right answer, what is the probability that C got their question wrong.

My logic behind this was finding AB(Not C) = 0.9*0.7*0.6, but apparently this is wrong. The correct answer was 0.7354

Any insight would be much appreciated. THanks!

It is conditional probability. You need to divide your answer by the probability that two of them got the right answer .....