What is the probability that a couple with four children have atleast one girl?

There are 2 ways to do this problem. 1. Go to a Binomial Distribution Table where n = 4 (4 children) and P=0.5(50% probability of a girl). Probability of at least 1 girl = 1 - probability of no girls. From Binomial Distribution Table n = 0 probability is .0625. So, 1 - 0.0625 = .9375 = probability of at least 1 girl. 2. The other way is to list all the possible ways to have 4 children and count the number of ways at least 1 girl exists divided by the total number of ways to have 4 children. There are 42 ways to have 4 children, all 16 listed below: bbbb bbbg bbgb bgbb gbbb bbgg bggb ggbb gbbg gbgb bgbg bggg gggb ggbg gbgg gggg Since 15 of the 16 have at least 1 girl, the Probability of at least 1 girl = 15/16 = 0.9375, the same answer as above.