a man has $4$ children, given that atleast one of whom is a girl.Find the probability that he has $3$ girls and $1$ boy.
MY TRY :
probability of girl=$1/4$ and probability of boy=$3/4$ (my doubt is here, are these two probabiity correct? because it is said that
atleast one of whom is a girl , not exactly 1)
=> 4c3 * (1/4)^4 * 3/4