GRE Prep 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.
GRE Prep Club Team Member
Joined: 20 Feb 2017
Posts: 2508
Given Kudos: 1053
GPA: 3.39
If the probability that Stock A will increase in value during the next
[#permalink]
17 Nov 2021, 03:13
17 Nov 2021, 03:13
Expert Reply
1
Bookmarks
00:00
Question Stats:
0% (00:00) correct
100% (00:56) wrong based on 2 sessions
Hide Show timer Statistics
If the probability that Stock A will increase in value during the next month is 0.54, and the probability that Stock B will increase in value during the next month is 0.68. What is the greatest value for the probability that neither of these two events will occur?
A. 0.22
B. 0.32
C. 0.37
D. 0.46
E. 0.63
A. 0.22
B. 0.32
C. 0.37
D. 0.46
E. 0.63
Retired Moderator
Joined: 09 Nov 2021
Status:GRE Tutor London and Online
Affiliations: Private GMAT/GRE Tutor London
Posts: 76
Given Kudos: 6
If the probability that Stock A will increase in value during the next
[#permalink]
18 Nov 2021, 05:26
18 Nov 2021, 05:26
1
Start with plain language: we want the probability that neither A nor B will occur, which is equivalent to saying that we have not-A AND not-B.
In formal notation:
P(-(AvB)) = P((-A)^(-B))
The probability of not-A is simply the inverse: 1-0.54 = 0.46
The probability of not-B is simply the inverse: 1-0.68 = 0.32
The probability of both together is P((-A)^(-B)) = P(-A)*P(-B) = 0.46*0.32, but that isn't what the question is asking
.
Remember that we need BOTH to happen, and this is clear when it asks for the greatest value of the probability. In fact, we are limited by probability of not-B, because of we don't achieve not-B, we don't reach our goal.
Therefore, the greatest probability for reaching not-B will be our greatest probability that neither of the two will occur: that is, answer B.
This is pure concept, but you can get the answer extremely quickly if you see what the question is really asking.
In formal notation:
P(-(AvB)) = P((-A)^(-B))
The probability of not-A is simply the inverse: 1-0.54 = 0.46
The probability of not-B is simply the inverse: 1-0.68 = 0.32
The probability of both together is P((-A)^(-B)) = P(-A)*P(-B) = 0.46*0.32, but that isn't what the question is asking
.Remember that we need BOTH to happen, and this is clear when it asks for the greatest value of the probability. In fact, we are limited by probability of not-B, because of we don't achieve not-B, we don't reach our goal.
Therefore, the greatest probability for reaching not-B will be our greatest probability that neither of the two will occur: that is, answer B.
This is pure concept, but you can get the answer extremely quickly if you see what the question is really asking.
gmatclubot
If the probability that Stock A will increase in value during the next [#permalink]
18 Nov 2021, 05:26
Moderators:
