Question 1145774
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(a)  At given conditions, the probability to have at least 3 girls 


         P( to have at least 3 girls ) = P(3) + P(4) = {{{C[4]^3*(1/2)^3*(1/2)}}} + {{{C[4]^4*(1/2)^4}}} = {{{4*(1/2)^4}}} + {{{1*(1/2)^4}}} = {{{5/16}}}.    <U>ANSWER</U>



(b)  At given conditions, the probability to have at most 3 girls is equal

     to the COMPLEMENT of the probability to have 4 girls.


         P( to have at most 3 girls ) = 1 - P(4) = 1 - {{{(1/2)^4}}} = 1 - {{{1/2^4}}} = {{{1 - 1/16}}} = {{{15/16}}}.   <U>ANSWER</U>
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