Last visit was: 19 Jul 2024, 13:58 It is currently 19 Jul 2024, 13:58
Toolkit
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

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.

# The probability of a man hitting a bulls eye in one fire is

SORT BY:
Tags:
Show Tags
Hide Tags
Manager
Joined: 15 Jun 2010
Posts: 242
Own Kudos [?]: 1189 [38]
Given Kudos: 50
Concentration: Marketing
Schools:IE'14, ISB'14, Kellogg'15
Q47  V26 GMAT 2: 540  Q45  V19 GMAT 3: 580  Q48  V23
GPA: 3.2
WE 1: 7 Yrs in Automobile (Commercial Vehicle industry)
Manager
Joined: 05 Jul 2012
Posts: 53
Own Kudos [?]: 149 [16]
Given Kudos: 8
Location: India
Concentration: Finance, Strategy
GMAT Date: 09-30-2012
GPA: 3.08
WE:Engineering (Energy and Utilities)
Math Expert
Joined: 02 Sep 2009
Posts: 94421
Own Kudos [?]: 642360 [8]
Given Kudos: 86332
General Discussion
Manager
Joined: 23 Jan 2011
Posts: 83
Own Kudos [?]: 431 [0]
Given Kudos: 13
Re: The probability of a man hitting a bulls eye in one fire is [#permalink]
very helpful Bunuel/mandyr, need to revise the "at least" rule and this helps, thank you both
Intern
Joined: 15 Apr 2015
Posts: 2
Own Kudos [?]: [0]
Given Kudos: 114
The probability of a man hitting a bulls eye in one fire is [#permalink]
Bunuel wrote:
SOURH7WK wrote:
The probability of a man hitting a bulls eye in one fire is 1/4. What is the least number of times that the man should fire in order to take the probability of hitting the bulls eye at least once to more than 50%.

A. 5
B. 7
C. 3
D. 12
E. 6

OA will follow after few discussions

The probability that the man hits the bulls eye at least once in 2 tries is 1-(3/4)^2=7/16, so less than 1/2 (the probability of hitting the bulls eye at least once is 1 minus the probability of the opposite event, so the probability that the men misses in all 2 tries).

The probability that the man hits the bulls eye at least once in 3 tries is 1-(3/4)^3=37/64, so more than 1/2.

Hi Bunuel ,

In question it is mentioned that " at least once to more than 50%", is that the reason you have checked if the probability value is greater than or less than 1/2?

Thanks,
Bhavana
Math Expert
Joined: 02 Sep 2009
Posts: 94421
Own Kudos [?]: 642360 [0]
Given Kudos: 86332
Re: The probability of a man hitting a bulls eye in one fire is [#permalink]
bhavana31 wrote:
Bunuel wrote:
SOURH7WK wrote:
The probability of a man hitting a bulls eye in one fire is 1/4. What is the least number of times that the man should fire in order to take the probability of hitting the bulls eye at least once to more than 50%.

A. 5
B. 7
C. 3
D. 12
E. 6

OA will follow after few discussions

The probability that the man hits the bulls eye at least once in 2 tries is 1-(3/4)^2=7/16, so less than 1/2 (the probability of hitting the bulls eye at least once is 1 minus the probability of the opposite event, so the probability that the men misses in all 2 tries).

The probability that the man hits the bulls eye at least once in 3 tries is 1-(3/4)^3=37/64, so more than 1/2.

Hi Bunuel ,

In question it is mentioned that " at least once to more than 50%", is that the reason you have checked if the probability value is greater than or less than 1/2?

Thanks,
Bhavana

Yes, more than 50% means more than 1/2.
GMAT Club Legend
Joined: 18 Aug 2017
Posts: 8009
Own Kudos [?]: 4242 [6]
Given Kudos: 243
Location: India
Concentration: Sustainability, Marketing
GMAT Focus 1:
545 Q79 V79 DI73
GPA: 4
WE:Marketing (Energy and Utilities)
Re: The probability of a man hitting a bulls eye in one fire is [#permalink]
4
Kudos
2
Bookmarks
SOURH7WK wrote:
The probability of a man hitting a bulls eye in one fire is 1/4. What is the least number of times that the man should fire in order to take the probability of hitting the bulls eye at least once to more than 50%.

A. 5
B. 7
C. 3
D. 12
E. 6

1/4 * x >50/100
or say
x>2
IMO C; 3
Non-Human User
Joined: 09 Sep 2013
Posts: 34026
Own Kudos [?]: 853 [0]
Given Kudos: 0
Re: The probability of a man hitting a bulls eye in one fire is [#permalink]
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: The probability of a man hitting a bulls eye in one fire is [#permalink]
Moderator:
Math Expert
94421 posts