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 350,000 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:

An exam consists of 8 true/false questions. Brian forgets to [#permalink]
23 Jul 2014, 21:18

7

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

55% (hard)

Question Stats:

61% (03:15) correct
39% (01:50) wrong based on 85 sessions

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

Re: An exam consists of 8 true/false questions. Brian forgets to [#permalink]
23 Jul 2014, 21:34

1

This post received KUDOS

maggie27 wrote:

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

A) 1/16 B) 37/256 C) 1/2 D) 219/256 E) 15/16

Since 70% is the passing rate, .70 ( 8 questions) = 5.6 correct answers (or 6 rounded up)

We must then look for the probability of passing: All correct answers + 7 correct answers + 6 correct answers = probability of passing.

All correct answers = \(\frac{1}{2}^8=\frac{1}{256}\)

An exam consists of 8 true/false questions. Brian forgets to [#permalink]
24 Jul 2014, 07:49

maggie27 wrote:

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

A) 1/16 B) 37/256 C) 1/2 D) 219/256 E) 15/16

I am not sure if the wording of the question is accurate. Anyone else feels the same way?

There are only two possibilities - Either Brian fails or he passes. So, probability that Brian passes = 1/2

Did I read the question incorrectly or is the wording ambiguous?

An exam consists of 8 true/false questions. Brian forgets to [#permalink]
24 Jul 2014, 07:56

1

This post received KUDOS

Expert's post

Game wrote:

maggie27 wrote:

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

A) 1/16 B) 37/256 C) 1/2 D) 219/256 E) 15/16

I am not sure if the wording of the question is accurate. Anyone else feels the same way?

There are only two possibilities - Either Brian fails or he passes. So, probability that Brian passes = 1/2

Did I read the question incorrectly or is the wording ambiguous?

No, that's not correct. According to your logic the probability of me dating Charlize Theron is also 1/2. Either yes or no. Wish this was true. _________________

Re: An exam consists of 8 true/false questions. Brian forgets to [#permalink]
24 Jul 2014, 17:20

Bunuel wrote:

Game wrote:

maggie27 wrote:

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

A) 1/16 B) 37/256 C) 1/2 D) 219/256 E) 15/16

I am not sure if the wording of the question is accurate. Anyone else feels the same way?

There are only two possibilities - Either Brian fails or he passes. So, probability that Brian passes = 1/2

Did I read the question incorrectly or is the wording ambiguous?

No, that's not correct. According to your logic the probability of me dating Charlize Theron is also 1/2. Either yes or no. Wish this was true.

OK. Got it. On a side note, probability of you dating Charlize Theron is 0 & here is the mathematical explanation for the math expert:

Assuming Charlize Theron (C.T.) will date only one person at a time Probability(Game dating C.T.) + Probability(Bunuel dating C.T.) + ... = 1 Since Probability(Game dating C.T.) = 1 Probability(Bunuel dating C.T.) + ... = 1 - 1 = 0

An exam consists of 8 true/false questions. Brian forgets to [#permalink]
09 Aug 2014, 14:54

1

This post was BOOKMARKED

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

Re: An exam consists of 8 true/false questions. Brian forgets to [#permalink]
09 Aug 2014, 16:02

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

If you have 8 T or F and Brian is going to guess then each question he has a 50% chance of getting correct.

If a passing score is 70% it means Brian needs to get 6/8=75%, 7/8=87.5%, or 8/8=100% to pass. Each is a possibility. If Brian gets a 5/8(=62.5%) or below he fails.

So first figure out the number of ways that Brian can get 6 out of 8, 7 out of 8, and 8 out of 8 questions correct. Which is 8 choose 6, equals is 28, 8 choose 7, equals 8, and 8 choose 8, equals 1. This sums to 37.

The number of possible questions outcomes -the sum of 8 choose 8, 7 choose 8, 6 choose 8….2 choose 8, 1 choose 8, and 0 choose 8 is 256, so the chance of him passing is 37/256.

I know there is a shorter way, but this is how I did it in about 2:34

Re: An exam consists of 8 true/false questions. Brian forgets to [#permalink]
10 Aug 2014, 00:35

2

This post received KUDOS

If you have True or False question, then each question has a \(\frac{1}{2}\) chance of getting correct.

If a passing score is 70% it means Brian needs to get right or 6 questions (6/8=75%), or 7 questions (7/8=87.5%), or 8 questions (8/8=100%).

The probability to have all 8 questions right is: \(\frac{1}{2^8}\) The probability to have 7 questions right and 1 wrong is: \(C_8^1*\frac{1}{2^7}*\frac{1}{2}=\frac{8}{2^8}\) (choose this incorrect answer \(C_8^1\), probability to have 7 right \(\frac{1}{2^7}\), and probability to have 1 wrong \(\frac{1}{2}\)) The probability to have 6 questions right and 2 wrong is: \(C_8^2*\frac{1}{2^6}*\frac{1}{2^2}=\frac{28}{2^8}\) (choose the se 2incorrect answers \(C_8^2\), probability to have 6 right \(\frac{1}{2^6}\), and probability to have 2 wrong \(\frac{1}{2^2}\))

The probability is \(\frac{1}{2^8}+\frac{8}{2^8}+\frac{28}{2^8}=\frac{37}{256}\) _________________

I'm happy, if I make math for you slightly clearer And yes, I like kudos:)

Re: An exam consists of 8 true/false questions. Brian forgets to [#permalink]
14 Dec 2014, 04:06

Bunuel wrote:

Game wrote:

maggie27 wrote:

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

A) 1/16 B) 37/256 C) 1/2 D) 219/256 E) 15/16

I am not sure if the wording of the question is accurate. Anyone else feels the same way?

There are only two possibilities - Either Brian fails or he passes. So, probability that Brian passes = 1/2

Did I read the question incorrectly or is the wording ambiguous?

No, that's not correct. According to your logic the probability of me dating Charlize Theron is also 1/2. Either yes or no. Wish this was true.

I have a very basic and silly doubt Why the probability of getting 7 right is 8c1/(1/2^8)

I mean i understood the denominator part but why 8c1? As it has to be 7 answers out of 8... So i thought it will be 2^7/2^8

Re: An exam consists of 8 true/false questions. Brian forgets to [#permalink]
15 Dec 2014, 06:26

Expert's post

gauriranjekar wrote:

I have a very basic and silly doubt Why the probability of getting 7 right is 8c1/(1/2^8)

I mean i understood the denominator part but why 8c1? As it has to be 7 answers out of 8... So i thought it will be 2^7/2^8

Please help..!!

Because 7 correct out of 8 can occur in 8 ways: YYYYYYYN (first 7 correct and 8th not). YYYYYYNY YYYYYNYY YYYYNYYY YYYNYYYY YYNYYYYY YNYYYYYY NYYYYYYY _________________

Re: An exam consists of 8 true/false questions. Brian forgets to [#permalink]
26 Jan 2015, 03:28

Expert's post

maggie27 wrote:

An exam consists of 8 true/false questions. Brian forgets to study, so he must guess blindly on each question. If any score above 70% is a passing grade, what is the probability that Brian passes?

First, Brian must get 70% of the 8 questions right to pass. 70% of 8 is 5.6, though, so he must get 6 questions right (there's no such thing as "partial credit" on a true/false question). This leaves us with three possible outcomes:

6 right, 2 wrong

7 right, 1 wrong

8 right, 0 wrong

We can use our knowledge of permutations with identical elements to calculate the probability here since, for our purposes, a correct answer on the first question is the same as a correct answer on the third question. Thus, there are 8!/(6!2!), or 28, ways to get 6 questions right, 8!/7!, or 8, ways to get 7 questions right, and only 1 way to get all 8 of the questions right. Brian has a total of 37 good outcomes. The number of possible outcomes, though, is 2^8, or 256, giving Brian a 37/256 chance of passing. Good luck, Brian!

I was checking my phone all day. I wasn’t sure when I would receive the admission decision from Tepper. I received an acceptance from Goizueta in the early morning...

This an overview of my journey till now! I started bloging in August last year. I had a nice list before getting started for GMAT studies. I took my first GMAT prep...

How should business schools teach public policy? On Wednesday, 22nd April 2015, between 2 - 3pm BST , two experts will answer readers' questions on the importance of integrating politics...