Suppose we pick 3 students at random from a class with 10 boys and 15 girls. let x be the number of boys selected and y be the number of girls selected. find e(x-y
The probability of the first pick to be a boy is 10/25. Let S be the sample space and E be the event of selecting 1 girl and 2 boys. n(S)=number of ways selecting students of 25. =²⁵C₃ =25·24·23/3·2·1 =2300 n(E)=(¹⁰C₁·¹⁵C₂) =[10·(15·14)/2·1 =10500 P(E)=n(E)/n(S)=1050/2300=21/46
