DrTacoElf said:

OMG, your a life saver

now why did you multiply the individual probabilites instead of add?

This is a concept i've been confused about for some time kinda.

You have to recall one of the Probability Rules: The Multiplication Rule.

The multiplication rule states that the probability of a compound event is equal to the multiple of the probabilities of the separate parts of the event.

A compound event is a multiple-part event... (like flipping a coin twice).

By multiplying (like Mr Reddly showed), we extract the number of successes in the numerator, and the number of possible outcomes in the denominator.

Can't explain more than that... but I can give you a different example:

Let's use a deck of cards for example... and let's just say we need to find the probability of getting a "Queen" then a "Jack", so... to apply the rule above:

This probability will then be... p|queen then Jack| - p|Queen| * p|Jack|