This video covers GMAT Probability Questions. Thoroughly study it and Ace the GMAT!
GMAT Probability Questions [Video Transcript]
In this lesson, we’ll examine various strategies you should consider when tackling probability questions. One of the first things to consider is whether the question can be solved faster by using the complement.
So rather than focus on the probability an event occurs, it may be faster to focus on the probability an event does not occur. Next you should decide which general approach to take. So you may choose to apply the basic probability formula or apply one or more of the probability rules.
If you choose to use the basic probability formula, you should confirm that the outcomes are equally likely. If the outcomes are not equally likely, you cannot use this formula. Now to apply the basic probability formula, you’ll need to count outcomes. To do so you can either list the outcomes or apply various counting techniques.
Now if you decide to use one or more of the probability rules, it might be useful to first rewrite the question by asking what must occur in order to achieve the target outcome. You’ll find that rewriting the question will often help you determine whether you need to use ‘and probabilities’ or ‘or probabilities,’ or both.
If the solution involves an ‘or probability,’ determine whether the events are mutually exclusive by asking the question “can both events occur together? ” If the answer is yes, then then events are not mutually exclusive and you should use this formula. If the answer is no, then the events are mutually exclusive and you should use this formula.
Now if the solution involves an ‘and probability,’ determine whether the events are independent by asking “does the occurrence of one event affect the probability of the other event? ” If the answer is yes, then the events are dependent and you should use this formula. And if the answer if no, then the events are independent and you should use this formula.
And that’s about it. If you follow these strategies, you’ll greatly increase your likelihood of success with probability questions.