quiz consists of 7 multiple choice questions. each question has 5 answers, one of which is correct. if random guess is made, find the probability that 3 answers will be correct and 4 wrong
this is binary ... right or wrong
p(r) = .2 ... p(w) = .8
(r + w)^7 = r^7 + 7 r^6 w + ... + 35 r^3 w^4 + ...
p(3 r , 4 w) = 35 * .2^3 * .8^4