What is the probability of selecting a boy and a girl if their are 7 girls and 3 boys.
are you only selecting two?
then it could be BG or GB
prob of that is 7/10 x 3/9 + 3/10 x 7/9
= 21/90 + 21/90 = 21/45
or C(7,1)xC(3,1)/C(10,2) = 21/45
then it could be BG or GB
prob of that is 7/10 x 3/9 + 3/10 x 7/9
= 21/90 + 21/90 = 21/45
or C(7,1)xC(3,1)/C(10,2) = 21/45