It is currently 14 Dec 2019, 16:48
My Tests

Close

GMAT Club Daily Prep

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.

When a coin is flipped, the probability of getting heads is

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Founder
Founder
User avatar
Joined: 18 Apr 2015
Posts: 9036
Followers: 180

Kudos [?]: 2143 [0], given: 8371

CAT Tests
When a coin is flipped, the probability of getting heads is [#permalink] New post 13 Mar 2019, 12:10
Expert's post
00:00

Question Stats:

78% (01:57) correct 21% (01:07) wrong based on 51 sessions
When a coin is flipped, the probability of getting heads is 0.5, and the probability of getting tails is 0.5 A coin is flipped 5 times.

Quantity A
Quantity B
Probability of getting exactly 2 heads
Probability of getting exactly 3 heads



A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.
[Reveal] Spoiler: OA

_________________

Need Practice? 20 Free GRE Quant Tests available for free with 20 Kudos
GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests.

1 KUDOS received
GRE Instructor
User avatar
Joined: 10 Apr 2015
Posts: 2632
Followers: 96

Kudos [?]: 2850 [1] , given: 45

CAT Tests
Re: When a coin is flipped, the probability of getting heads is [#permalink] New post 16 Mar 2019, 06:23
1
This post received
KUDOS
Expert's post
Carcass wrote:
When a coin is flipped, the probability of getting heads is 0.5, and the probability of getting tails is 0.5 A coin is flipped 5 times.

Quantity A
Quantity B
Probability of getting exactly 2 heads
Probability of getting exactly 3 heads



A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.


Since P(heads) = P(tails), we know that:
P(0 HEADS in 5 flips) = P(0 TAILS in 5 flips)
P(1 HEAD in 5 flips) = P(1 TAIL in 5 flips)
P(2 HEADS in 5 flips) = P(2 TAILS in 5 flips)
P(3 HEADS in 5 flips) = P(3 TAILS in 5 flips)
P(4 HEADS in 5 flips) = P(4 TAILS in 5 flips)
P(5 HEADS in 5 flips) = P(5 TAILS in 5 flips)

Now notice that getting 2 TAILS in 5 flips is exactly the same as getting 3 HEADS in 5 flips [if 2 flips are tails, then the other 3 flips must be heads]

So, we can write: P(2 HEADS in 5 flips) = P(2 TAILS in 5 flips) = = P(3 HEADS in 5 flips)

Answer: C

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com
Sign up for my free GRE Question of the Day emails

1 KUDOS received
Manager
Manager
Joined: 22 Aug 2019
Posts: 63
Followers: 0

Kudos [?]: 37 [1] , given: 11

Re: When a coin is flipped, the probability of getting heads is [#permalink] New post 09 Sep 2019, 18:50
1
This post received
KUDOS
Carcass wrote:
When a coin is flipped, the probability of getting heads is 0.5, and the probability of getting tails is 0.5 A coin is flipped 5 times.

Quantity A
Quantity B
Probability of getting exactly 2 heads
Probability of getting exactly 3 heads



A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.


concise why that I thought about this one is reading the question as "what's the probability of getting exactly 2 heads vs getting exactly 2 tails" Well, both sides have equal probability, so clearly it's going to be the same.

I'd be curious about how to do the math if the question was a bit more nuanced but I don't think that would be on the GRE. Right now my only thought would be to make a table of all possible answers (denominator) and then count how many acceptable answers there are (numerator).
Senior Manager
Senior Manager
User avatar
Joined: 22 Jun 2019
Posts: 391
Followers: 0

Kudos [?]: 56 [0], given: 148

CAT Tests
Re: When a coin is flipped, the probability of getting heads is [#permalink] New post 28 Oct 2019, 19:56
In Magoosh, it,s a hard question not medium.
Re: When a coin is flipped, the probability of getting heads is   [#permalink] 28 Oct 2019, 19:56
Display posts from previous: Sort by

When a coin is flipped, the probability of getting heads is

  Question banks Downloads My Bookmarks Reviews Important topics  


GRE Prep Club Forum Home| About| Terms and Conditions and Privacy Policy| GRE Prep Club Rules| Contact

Powered by phpBB © phpBB Group

Kindly note that the GRE® test is a registered trademark of the Educational Testing Service®, and this site has neither been reviewed nor endorsed by ETS®.