It is currently 23 Nov 2017, 02:43

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

The probability of shooting a target increases after a

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
1 KUDOS received
Director
Director
User avatar
B
Joined: 17 Dec 2012
Posts: 623

Kudos [?]: 535 [1], given: 16

Location: India
The probability of shooting a target increases after a [#permalink]

Show Tags

New post 18 Mar 2013, 07:03
1
This post received
KUDOS
Expert's post
8
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

33% (01:26) correct 67% (01:12) wrong based on 183 sessions

HideShow timer Statistics

The probability of shooting a target increases after a certain skill is enhanced and is equal to the new probability of NOT shooting the target. Given this fact, which of the following must be false?

A. The new probability of shooting the target is greater than 0.5
B. The original probability of shooting the target is less than 0.5
C. The original probability of NOT shooting the target and the new probability of shooting the target are the same
D. The original probability of shooting the target and that of NOT shooting the target are the same.
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1.
[Reveal] Spoiler: OA

_________________

Srinivasan Vaidyaraman
Sravna
http://www.sravnatestprep.com/regularcourse.php

Premium Material
Standardized Approaches

Kudos [?]: 535 [1], given: 16

2 KUDOS received
Manager
Manager
User avatar
Joined: 24 Jan 2013
Posts: 77

Kudos [?]: 155 [2], given: 6

Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 20 Mar 2013, 03:12
2
This post received
KUDOS
Quote:
The probability of shooting a target increases after a certain skill is enhanced and is equal to the new probability of NOT shooting the target. Given this fact, which of the following must be false?


I think this is a 700 problem.

If I understood well the question, we have:

  • initial probability of shooting target: \(P(success\;initial)\)
  • initial probability of not shooting the target: \(P(not\;success\;initial)\)
  • new probability of shooting target: \(P(success\;final)\)
  • new probability of not shooting the target: \(P(not\;success\;final)\)

Conditions given by problem:

(1) \(P(success\;initial)=1-P(not\;success\;initial)\)

(2) \(P(success\;final)=1-P(not\;success\;final)\)

(3) \(P(success\;initial)<P(success\;final)\)

(4) \(P(success\;initial)=P(not\;success\;final)\)

Therefore:

\(P(success\;final)=1-P(success\;initial)\)

then

\(P(success\;initial)<1-P(success\;initial)\) ---> \(P(success\;initial)<0.5\)

Conclusions:

(5) \(P(success\;initial)<0.5\)

(6) \(P(success\;final)>0.5\)

(7) \(P(not\;success\;final)<0.5\)

(8) \(P(not\;success\;initial)>0.5\)

(9) \(P(success\;final)=1-P(not\;success\;final)\) ---> \(P(success\;final)=1-P(success\;initial)\) ---> \(P(success\;final)+P(success\;initial)=1\)

Analysis of different options:

A. The new probability of shooting the target is greater than 0.5: TRUE, look at (6)
B. The original probability of shooting the target is less than 0.5: TRUE, look at (5)
C. The original probability of NOT shooting the target and the new probability of shooting the target are the same: TRUE, look at (4)
D. The original probability of shooting the target and that of NOT shooting the target are the same: FALSE
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1: : TRUE, look at (9)

Kudos [?]: 155 [2], given: 6

Manager
Manager
User avatar
Joined: 24 Jan 2013
Posts: 77

Kudos [?]: 155 [0], given: 6

Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 20 Mar 2013, 08:45
In fact, the key formula here to solve the whole problem is:

\(P(A)=1-P(not\;A)\)

Then differentiate between the initial situation and the new (or final) situation:

Initial: \(P(A)=1-P(not\;A)\)

New: \(P(Z)=1-P(not\;Z)\)

And link the formulas with the conditions given by the problem.

Kudos [?]: 155 [0], given: 6

Expert Post
Director
Director
User avatar
B
Joined: 17 Dec 2012
Posts: 623

Kudos [?]: 535 [0], given: 16

Location: India
Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 24 Mar 2013, 19:07
SravnaTestPrep wrote:
The probability of shooting a target increases after a certain skill is enhanced and is equal to the new probability of NOT shooting the target. Given this fact, which of the following must be false?

A. The new probability of shooting the target is greater than 0.5
B. The original probability of shooting the target is less than 0.5
C. The original probability of NOT shooting the target and the new probability of shooting the target are the same
D. The original probability of shooting the target and that of NOT shooting the target are the same.
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1.



1. Let p(i), q(i), be the initial probability of shooting and missing the target respectively and let p(n) and q(n) be the new probability of shooting and missing the target respectively.

Given:

1. p(i) + q(i) =1
2. P(n) + q(n) =1
3. p(n) > p(i)
4. p(i) = q(n)

Deductions:

5. q(n) + q(i) =1 ( from (1) and (4) )
6. p(n) + p(i) =1 ( from (2) and (4) ) - ( Choice E always true)

7. From ( 3) and (6), p(i) < 0.5 and p(n) > 0.5 - ( Choice A and Choice B always true)

8. From (1) and (6), q(i) = p(n) - ( Choice C always true)

9. From (3) and (8), q(i) > p(i) - ( choice D always false)

Therefore the answer is Choice D.
_________________

Srinivasan Vaidyaraman
Sravna
http://www.sravnatestprep.com/regularcourse.php

Premium Material
Standardized Approaches

Kudos [?]: 535 [0], given: 16

Current Student
User avatar
Joined: 06 Sep 2013
Posts: 1970

Kudos [?]: 745 [0], given: 355

Concentration: Finance
GMAT ToolKit User
Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 24 Mar 2014, 09:56
SravnaTestPrep wrote:
The probability of shooting a target increases after a certain skill is enhanced and is equal to the new probability of NOT shooting the target. Given this fact, which of the following must be false?

A. The new probability of shooting the target is greater than 0.5
B. The original probability of shooting the target is less than 0.5
C. The original probability of NOT shooting the target and the new probability of shooting the target are the same
D. The original probability of shooting the target and that of NOT shooting the target are the same.
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1.


Sravna, what's the source of this question?

I find a little bit out of scope of GMAT

Thanks
Cheers
J

Kudos [?]: 745 [0], given: 355

Senior Manager
Senior Manager
User avatar
B
Joined: 08 Jun 2015
Posts: 327

Kudos [?]: 21 [0], given: 101

Location: India
GMAT 1: 640 Q48 V29
Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 20 May 2016, 08:05
Can you specify the source of this question ? Further, is there an easier way to solve the question ? Listing out the nine cases is time consuming !
_________________

" The few , the fearless "

Kudos [?]: 21 [0], given: 101

Manager
Manager
User avatar
Joined: 27 Apr 2016
Posts: 93

Kudos [?]: 11 [0], given: 12

Location: Brazil
GMAT 1: 610 Q37 V36
GPA: 2.7
WE: Information Technology (Education)
Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 20 May 2016, 14:28
I always get these questions right, but I take a lot of time!!

I took 3:20 to answer this one. How can I improve this specific aspect??
_________________

The errant cosmos works against me!

Kudos [?]: 11 [0], given: 12

Director
Director
User avatar
G
Joined: 13 Mar 2017
Posts: 552

Kudos [?]: 134 [0], given: 64

Location: India
Concentration: General Management, Entrepreneurship
GPA: 3.8
WE: Engineering (Energy and Utilities)
Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 07 Aug 2017, 22:51
SravnaTestPrep wrote:
The probability of shooting a target increases after a certain skill is enhanced and is equal to the new probability of NOT shooting the target. Given this fact, which of the following must be false?

A. The new probability of shooting the target is greater than 0.5
B. The original probability of shooting the target is less than 0.5
C. The original probability of NOT shooting the target and the new probability of shooting the target are the same
D. The original probability of shooting the target and that of NOT shooting the target are the same.
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1.


Original :
Let the probability of shooting the target be x. So, probability of not shooting the target will be 1-x
Similarly for new probability. Let the probability of shooting the target be y. So, probability of not shooting the target be 1-y
Now x = 1-y as per questiosn stem

So, x+ y = 1. SO y = 1-x

Original : P (Shooting) = x, P (not shooting) = 1-x
New : P (Shooting) = y = 1-x, P (not shooting) = 1-y = x.

Lets come to the option now.
A. The new probability of shooting the target is greater than 0.5. Yes it is true. Since new probability increase so, earlie it must be smaller than 0.5 and now it muct have increased above 0.5
B. The original probability of shooting the target is less than 0.5. Yes it is true due to same reason as described in A.
C. The original probability of NOT shooting the target i.e. 1-x and the new probability of shooting the target i.e. 1-x are the same. yes it is true.
D. The original probability of shooting the target and that of NOT shooting the target are the same. NO This is not true. original proabability of shooting the target is x andn NOT shooting the target is 1-x . both are not same.
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1. x+ y = 1. Yes it is TRUE.

Answer D.
Though it took lots of time to figure it out.
_________________

MBA Social Network : WebMaggu

Appreciate by Clicking +1 Kudos ( Lets be more generous friends.)

Kudos [?]: 134 [0], given: 64

VP
VP
avatar
S
Joined: 12 Dec 2016
Posts: 1135

Kudos [?]: 22 [0], given: 1087

Location: United States
GMAT 1: 700 Q49 V33
GPA: 3.64
GMAT ToolKit User Premium Member CAT Tests
Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 30 Aug 2017, 11:26
A,B are correct
C is right because both the new and the original of NOT shooting are same
E is based on the same logic with C.

Kudos [?]: 22 [0], given: 1087

Intern
Intern
avatar
B
Joined: 30 Aug 2017
Posts: 4

Kudos [?]: 1 [0], given: 5

Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 30 Aug 2017, 12:08
SravnaTestPrep wrote:
The probability of shooting a target increases after a certain skill is enhanced and is equal to the new probability of NOT shooting the target. Given this fact, which of the following must be false?

A. The new probability of shooting the target is greater than 0.5
B. The original probability of shooting the target is less than 0.5
C. The original probability of NOT shooting the target and the new probability of shooting the target are the same
D. The original probability of shooting the target and that of NOT shooting the target are the same.
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1.


Can someone explain the following? If the skill is enhanced and is equal to the new probability of NOT shooting the target, then assuming A is correct the sum of both would be greater 1. So how can A be correct?

It should be equal to not greater than. Assuming its a binomial distribution.

Kudos [?]: 1 [0], given: 5

VP
VP
avatar
S
Joined: 12 Dec 2016
Posts: 1135

Kudos [?]: 22 [0], given: 1087

Location: United States
GMAT 1: 700 Q49 V33
GPA: 3.64
GMAT ToolKit User Premium Member CAT Tests
Re: The probability of shooting a target increases after a [#permalink]

Show Tags

New post 30 Aug 2017, 22:53
nmargot wrote:
SravnaTestPrep wrote:
The probability of shooting a target increases after a certain skill is enhanced and is equal to the new probability of NOT shooting the target. Given this fact, which of the following must be false?

A. The new probability of shooting the target is greater than 0.5
B. The original probability of shooting the target is less than 0.5
C. The original probability of NOT shooting the target and the new probability of shooting the target are the same
D. The original probability of shooting the target and that of NOT shooting the target are the same.
E. The sum of the original and the new probabilities of shooting the target is ALWAYS equal to 1.


Can someone explain the following? If the skill is enhanced and is equal to the new probability of NOT shooting the target, then assuming A is correct the sum of both would be greater 1. So how can A be correct?

It should be equal to not greater than. Assuming its a binomial distribution.


Let original probability of shooting a target = a

ORIGINAL probability of NOT shooting the target = NEW probability of NOT shooting the target = b = NEW probability of shooting a target

=> a + b = 1

Kudos [?]: 22 [0], given: 1087

Re: The probability of shooting a target increases after a   [#permalink] 30 Aug 2017, 22:53
Display posts from previous: Sort by

The probability of shooting a target increases after a

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.