Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: : What is the probability that event E or event F or both w [#permalink]

Show Tags

18 Mar 2011, 07:05

bogos wrote:

If we agree that 1. (E OR F) means E, or F, or both will occur 2. (E AND F) means both will occur

then we have (see MGMAT Guide 4 page 87)

P(E OR F) = P(E) + P(F) - P(E AND F)

Here P(E AND F) is not given, so the answer is E.

P(E OR F) = P(E) + P(F) - P(E AND F) is true if E and F are dependent events.However if they are independent Events P(E OR F) = P(E) + P(F) .Question does not provide information ..whether E and F are dependent/ independent event ...so it should be E

Re: : What is the probability that event E or event F or both w [#permalink]

Show Tags

18 Mar 2011, 09:00

The formula is always true. MGMAT just clarifies the point by seperating the two cases. In fact, we have: P(E AND F) = 0 if E and F are independent. _________________

Re: : What is the probability that event E or event F or both w [#permalink]

Show Tags

18 Mar 2011, 11:18

Quote:

P(E AND F) = 0 if E and F are independent.

Not true, P(E AND F) = 0 if E and F are MUTUALLY EXCLUSIVE.

To say that E and F are independent means only that the outcome of E has no effect on the outcome of F and vice versa.

Quote:

P(E OR F) = P(E) + P(F) - P(E AND F) is true if E and F are dependent events.However if they are independent Events P(E OR F) = P(E) + P(F)

If they are independent events you still need the -P(E and F)

For example: If you flip two coins (coins 1 and 2) at the same time, and we call the event that coin 1 lands heads "E" and the event the coin 2 lands heads "F", what is P(E or F)?

Ifor example, if two coins are flipped the chance of both being heads is [18]

Mutually exclusive If either event A or event B or both events occur on a single performance of an experiment this is called the union of the events A and B denoted as .

For example, the chance of rolling a 1 or 2 on a six-sided die is

This is from Wikipedia. I found this when I was searching for the explanation for this question. But I am still confused the difference between independent probability and mutually exclusive. To me, they sound the same. Help me understand them.

Re: What is the probability that event E or event F or both will [#permalink]

Show Tags

14 Jan 2014, 02:39

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Re: What is the probability that event E or event F or both will [#permalink]

Show Tags

28 Jan 2014, 05:22

1

This post received KUDOS

Mountain14 wrote:

Hi Bunuel,

I am not clear why E is the answer...

we have to find P(E)+P(F) + P(EUF), so using Stm1 and Stm 2, we should be able to find.

i.e 0.6 +0.4 + ( 0.6x0.4)...

So, Isn't the answer should be C

Thanks

I'm not Bunuel but I'm sure I can help

P (A and B) = P(A) * P (B/A). That means the probability of B given that A happens. Now only way that the second term is equal to P(B) is if they are independent events, otherwise the probability will be affected. For instance if you have some balls to pick from and you remove some and don't replace them then successive probabilities will change right? So back to the question, Are they independent events? We just don't know this.

Hope it helps brother Cheers! K

PS. Just as a side note check also Mutually exclusive events in the GMAT Club Math Book just to be clear with those Probability concepts

Re: What is the probability that event E or event F or both will [#permalink]

Show Tags

28 Jan 2014, 06:34

Hi we have no information weather E and F are independent events. So we cant answer the question even by considering the two choices So ans should be E

Re: What is the probability that event E or event F or both will [#permalink]

Show Tags

10 Mar 2015, 02:44

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Re: What is the probability that event E or event F or both will [#permalink]

Show Tags

17 Mar 2016, 18:28

banksy wrote:

What is the probability that event E or event F or both will occur?

(1) The probability that event E will occur is 0.6. (2) The probability that event F will occur is 0.4.

we are asked P(E or F) + P(E and B) usually, if the two events are mutually exclusive, then: P(E) + P(F)=1. - and P(E or F)=1, and P(E and F)=0. if not, then: P(E or F) = P(E) + P(F) + P(E and F) and P(E or F)+P(E and F) = P(E) + P(F)

moreover, it might be conditional probability...

1. P(E)=0.6, but we do not know anything about P(F), or about what kind of events these two are. Moreover, we do not know whether there are any relations between these two. not sufficient.

2. P(F)=0.4 - same as 1. so no

at this moment, we crossed A, B, and D. our chances of getting to the right answer increased considerably - probability 50% (see how I used probability even here? :D)

ok, so it might appear that the two events are independent, since P(E)+P(F)=1. but what if we have a conditional probability? what if F can be chosen only if E is chosen?

in this case, the probability of getting F is P(E)* # of successes/total outcomes left = 4/10 since we do not know the relationship between these two events, then we cannot give a definite answer.

E

gmatclubot

Re: What is the probability that event E or event F or both will
[#permalink]
17 Mar 2016, 18:28

So, my final tally is in. I applied to three b schools in total this season: INSEAD – admitted MIT Sloan – admitted Wharton – waitlisted and dinged No...

HBS alum talks about effective altruism and founding and ultimately closing MBAs Across America at TED: Casey Gerald speaks at TED2016 – Dream, February 15-19, 2016, Vancouver Convention Center...

By Libby Koerbel Engaging a room of more than 100 people for two straight hours is no easy task, but the Women’s Business Association (WBA), Professor Victoria Medvec...