Question

A student takes a true-false test consisting of 15 questions. assuming that the student guesses at each question, find the probability that the student answers exactly 13 questions correctly

Answer 1

there are two possible answers two each question T or F so it has 1/2 of a possiblity of succeding

and there are 15 questions so that gives 1/15 but we need 13 questions so 13/15

and because we need all thirteen to be correct we multiply both

so 13/15*1/2
which gives us 13/30