If the probability of a boy being born is 1/2, and a family plans to have four children, what are the odds against having all boys?


If the odds in favor of Fast Legs winning a horse race are 5 to 2 and the first prize is $14,000, what is the expected value of Fast Leg's winning?



How do I figure out these two problems and can you show me step for step and the answers? I have been working on these problems for two hours and I can't figure them out. Odds against/in favor of, and expected value is giving me a lot of trouble.

The first one is easy, there is only a single way to get 4 boys, so this one is easy. You multiply together the chance of getting a boy in each case.

I don't quite understand the second one...