From the course: Test Prep: GRE

Unlock the full course today

Join today to access over 23,200 courses taught by industry experts.

Either/or probability

Either/or probability

From the course: Test Prep: GRE

Start my 1-month free trial Buy for my team

Either/or probability

“

- [Voiceover] For either/or probability, let's think about, again, a mutually exclusive event. So let's think about this. By mutually exclusive, again, I mean two things that cannot both happen. Let's say what are the odds that I roll a six-sided die, and I roll either an even number or a five? Let's think about this, if we have mutually exclusive events, we just add the two probabilities together. So a lot of times, we call this probability of event one plus the probability of event number two. A lot of times, we use E and F for these. So what's the probability I roll an even number? That's gonna be three out of six. On a six-sided die, there's three even numbers. Then what is the probability I roll a five? Well, there's one five, so one out of six. If I add those, I get four out of six. Another way to think about this is our basic formula. Let me write that again for you here. On the bottom of the fraction, it's gonna be the number of total possibilities, and up on top is the number…

Contents