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.
Sep 0201:00 PM EDT
-11:59 PM EDT
Take 30% off all study plans with code COURSEWORK - Expires on Monday 9/7
Sep 0410:00 AM PDT
-11:00 AM PDT
What does test anxiety really look like on the GMAT? For many test takers, it does not look like a panic attack. Instead, it shows up as brain fog, rereading, negative comparisons, mental noise....
Sep 0410:00 AM EDT
-11:59 PM EDT
We’ve worked incredibly hard to build TTP into the best test prep experience possible, and it would mean a lot to us to win Newsweek’s 2026 Readers’ Choice Award for Best Test Prep. If TTP has helped you, we’d be incredibly grateful for your vote.
Sep 0609:30 AM EDT
-12:30 PM EST
Top scores are possible when you enroll in a powerful EA course, taught live online + 6 months access to TTP OnDemand video courses included! Perfect class schedule and easy course access for working professionals. Class starts Sundays Sept. 6, 2026.- Sep 07
12:01 AM PDT
-11:59 PM PDT
On the 7th, GMAT Club Tests will be Free! Including all the Quizzes, Questions, and Tests. 12 AM - 11:59 PM PDT - Sep 07
10:00 AM PDT
-11:00 AM PDT
A complete walkthrough of GMAT Club’s free 12-week GMAT study plan: what you study each week, how progress and goals are tracked, how the error log works, and how your practice unlocks paid tools at no cost. - Sep 09
07:00 AM PDT
-10:00 AM PDT
Meet AdComs and explore top Master’s programs - MiM, MiF, MSc, MSBA and more. - Application Fee Waivers - Free 1-Week of GMAT Club Tests: - Master's Application Toolkit - Grand Prize Giveaway - Sep 09
10:00 AM PDT
-11:00 AM PDT
Three MBA applications. Three rejections. No interview invites. A year later, Aman was admitted to Cambridge Judge, SMU, and IMD. In this episode of MBA Admit Stories, Aman shares how he rebuilt his MBA application... 
Sep 1507:00 PM EDT
-09:00 PM EST
Elite scores are possible when you enroll in a powerful GMAT course, taught live online + 6 months access to TTP OnDemand video courses included! Class starts Tues/Thurs Sept. 15, 2026 - Nov. 15, 2027, 7:00pm-9:00pm EST
Sep 2108:00 PM EDT
-10:00 PM EDT
Boost your GMAT score in less than one month in a live online class + 6 months access to TTP OnDemand video courses included! Class starts Mon, Tues, Wed, Thur, Fri Sept. 21, 2026 - Oct. 9, 2027, 7:00pm-10:00pm EST
28 Nov 2023, 08:05
Kudos
Bookmarks
Number of lots: 20
Desirable outcomes in B: 16
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
84% (02:11) correct
16%
(02:16)
wrong
based on 609
sessions
History
Date
Time
Result
Not Attempted Yet
During a lottery, several lots are to be selected. A is the event that a certain subset of these lots is selected, and B is the event that another subset of these lots is selected, such that:
• the probability of event A occurring is 2/5.
• the probability of event B occurring is 4/5.
• the probability of the union of events A and B occurring is 1.
• the intersection of events A and B is an event with four desirable outcomes.
In the following table, identify the total number of lots and the number of desirable outcomes in event B. Make only one selection in each column.
• the probability of event A occurring is 2/5.
• the probability of event B occurring is 4/5.
• the probability of the union of events A and B occurring is 1.
• the intersection of events A and B is an event with four desirable outcomes.
In the following table, identify the total number of lots and the number of desirable outcomes in event B. Make only one selection in each column.
| Number of lots | Desirable outcomes in B | |
| 15 | ||
| 16 | ||
| 17 | ||
| 18 | ||
| 19 | ||
| 20 |
ShowHide Answer
Official Answer
Number of lots: 20
Desirable outcomes in B: 16
01 Dec 2023, 08:12
Kudos
Bookmarks
Official Explanation
The probability of the union of events A and B occurring equals the probability of event A occurring, plus the probability of event B occurring, minus the probability of the intersection of events A and B occurring. You know the value of all of these probabilities except the last one. The probability of the intersection of events A and B equals the number of desirable outcomes in the intersection of A and B, which is 4, over the number of total outcomes in the lottery—let’s call that t. Thus, you have:
P (AUB) = P (A) + P (B) - P (A∩B)
\(1=\frac{2}{5}+\frac{4}{5}-\frac{4}{t}\)
\(1=\frac{2t-4t-20}{5t}\)
\(5t=6t-20\)
\(t=20\)
So the correct answer in the first column = the total number of lots is 20.
Next, let the number of desirable outcomes in event B be b. In that case, you have:
P(B)\(=\frac{b}{20}\)
\(\frac{4}{5}=\frac{b}{20}\)
\(4=\frac{b}{4}\)
\(b=16\)
So the correct answer in the second column is: the number of desirable outcomes in event B is 16.
The probability of the union of events A and B occurring equals the probability of event A occurring, plus the probability of event B occurring, minus the probability of the intersection of events A and B occurring. You know the value of all of these probabilities except the last one. The probability of the intersection of events A and B equals the number of desirable outcomes in the intersection of A and B, which is 4, over the number of total outcomes in the lottery—let’s call that t. Thus, you have:
P (AUB) = P (A) + P (B) - P (A∩B)
\(1=\frac{2}{5}+\frac{4}{5}-\frac{4}{t}\)
\(1=\frac{2t-4t-20}{5t}\)
\(5t=6t-20\)
\(t=20\)
So the correct answer in the first column = the total number of lots is 20.
Next, let the number of desirable outcomes in event B be b. In that case, you have:
P(B)\(=\frac{b}{20}\)
\(\frac{4}{5}=\frac{b}{20}\)
\(4=\frac{b}{4}\)
\(b=16\)
So the correct answer in the second column is: the number of desirable outcomes in event B is 16.
General Discussion
29 Nov 2023, 08:41
Kudos
Bookmarks
hi Sajjad1994, could you help to explain this question?
