Posted by Student on Sunday, March 4, 2012 at 2:28pm.
The answer is
(n,r)/2^n
Here there are 6 questions, so n=6, and
there are 2^6=64 possible sets of answers.
Since 4 of them are right, the number of combinations with 4 correct out of 6 is
(n,r)=(6,4)=6*5/(1*2)=15
What would be the probability that 4 out of six are correct if the answers are completely random?
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