A family has three children.
Total outcomes = GGG , GGB ,GBG ,BGG, BBB ,BBG, BGB ,GBB = 8
(A)
Exactly one girl = BBG,BGB,GBB
Probability = 3/8
(B)
Atleast One girl means
3 girl,2 girl or 1 girl.
=GGG,GGB,GBG,BGG,BBG,BGB,GBB
Probability = 7/8
(C )
At most one girl mean no girl or 1 girl
So, favourable outcomes = BBB, BBG, BGB, GBB = 4
probability = 4/8= 1/2