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.
Apr 2301:30 AM EDT
-02:30 AM EDT
Struggling with GMAT Verbal as a non-native speaker? Harsh improved his score from 595 to 695 in just 45 days—and scored a 99 %ile in Verbal (V88)! Learn how smart strategy, clarity, and guided prep helped him gain 100 points.
Apr 2212:30 AM EDT
-01:30 AM EDT
At one point, she believed GMAT wasn’t for her. After scoring 595, self-doubt crept in and she questioned her potential. But instead of quitting, she made the right strategic changes. The result? A remarkable comeback to 695. Check out how Saakshi did it.
Apr 2308:00 PM PDT
-09:00 PM PDT
Video explanations + diagnosis of 10 weakest areas + 150+ short videos + study plan!
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
06 Mar 2015, 07:25
Kudos
Bookmarks
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
43% (01:24) correct
57%
(01:24)
wrong
based on 866
sessions
History
Date
Time
Result
Not Attempted Yet
Suppose A and B are two events that are not independent. Is the probability P(A and B) > 1/3?
(1) P(A) = 0.8 and P(B) = 0.7
(2) P(A or B) = 0.9
(1) P(A) = 0.8 and P(B) = 0.7
(2) P(A or B) = 0.9
06 Mar 2015, 22:56
Kudos
Bookmarks
Answer should be A.
P(A U B) = P(A) + P(B) - P(A and B)
option A : P(A U B) = 0.8 + 0.7 - P(A and B) = 1.5 - P(A and B).
P(A U B) can not have value greater than 1, so, P(A and B) >= 0.5. Sufficient.
option B : Clearly Not Sufficient.
P(A U B) = P(A) + P(B) - P(A and B)
option A : P(A U B) = 0.8 + 0.7 - P(A and B) = 1.5 - P(A and B).
P(A U B) can not have value greater than 1, so, P(A and B) >= 0.5. Sufficient.
option B : Clearly Not Sufficient.
08 Mar 2015, 16:14
Kudos
Bookmarks
Bunuel
MAGOOSH OFFICIAL SOLUTION:
Statement #1: this is very tricky. There is no cut-and-dry probability rule for this. we have to think about overlap. The total probability space, which encompasses anything that possibly could happen, has a size of 1, and P(A) and P(B) have to fit in this space. These two have a size of 0.8 and 0.7 respectively, so they are going to overlap. Think about it visually —
Attachment:
gdspqop_img4.png [ 5.18 KiB | Viewed 24222 times ]
Push the P(A) = 0.8 all the way to the left (whatever that means!), leaving the 0.2 outside of A on the right. Now, push P(B) = 0.7 all the way to the right, leaving the 0.3 outside of B on the left. Suppose the 0.2 outside of A is inside B, and the 0.03 outside of B is inside A. This would be the minimum possible overlap, and even then the overlap, P(A and B), equals 0.5. Thus, P(A and B) ≥ 0.5, so it must be greater than 1/3. this statement allows us to give a definitive answer to the prompt question. This statement, alone and by itself, is sufficient.
Statement #2: forget everything we learned in the analysis of statement (1). Now, all we know is P(A or B) = 0.9, and we know absolutely nothing about P(A) or P(B). We can calculate nothing else. This statement, alone and by itself, is insufficient.
First sufficient, second not sufficient.
Answer = A.
