Forum Home > GMAT > Quantitative > Problem Solving (PS)
Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Dec 1410:00 AM EST
-12:00 PM EST
Think a 100% GMAT Verbal score is out of your reach? Target Test Prep will make you think again! Our course uses techniques such as topical study and spaced repetition to maximize knowledge retention and make studying simple and fun.
Dec 1411:00 AM IST
-01:00 PM IST
Attend this session to learn how to Deconstruct arguments, Pre-Think Author’s Assumptions, and apply Negation Test.
Dec 1310:00 AM EST
-12:00 PM EST
Have you ever wondered how to score a PERFECT 805 on the GMAT? Meet Julia, a banking professional who used the Target Test Prep course to achieve this incredible feat. Julia's story is nothing short of an inspiration.- Dec 15
11:00 AM IST
-01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease. 
Dec 1608:00 AM PST
-11:59 PM PST
GMAT Club 12 Days of Christmas is a 4th Annual GMAT Club Winter Competition based on solving questions. This is the Winter GMAT competition on GMAT Club with an amazing opportunity to win over $40,000 worth of prizes!- Dec 17
09:00 AM PST
-10:00 AM PST
Join Manhattan Prep instructor Whitney Garner for a fun—and thorough—review of logic-based (non-math) problems, with a particular emphasis on Data Sufficiency and Two-Parts. - Dec 18
10:00 AM PST
-11:00 AM PST
Here is the essential guide to securing scholarships as an MBA student! In this video, we explore the various types of scholarships available, including need-based and merit-based options.
18 Mar 2013, 07:03
Kudos
Bookmarks
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
37% (01:59) correct
63%
(01:50)
wrong
based on 193
sessions
History
Date
Time
Result
Not Attempted Yet
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.
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.
20 Mar 2013, 03:12
Kudos
Bookmarks
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)
20 Mar 2013, 08:45
Kudos
Bookmarks
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.
\(P(A)=1-P(not\;A)\)
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.
