Last visit was: 25 Apr 2026, 02:26 It is currently 25 Apr 2026, 02:26
Home
Messages
Tests
Schools
Events
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 25 Apr 2026
Posts: 109,822
Own Kudos:
811,130
 [7]
Given Kudos: 105,878
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,822
Kudos: 811,130
 [7]
The probability that team A will not win the tournament is 80% and the 20 Mar 2018, 23:29
Kudos
Add Kudos
6
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
D
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:

73% (01:09) correct 27% (01:29) wrong based on 311 sessions

History

Date
Time
Result
Not Attempted Yet
The probability that team A will not win the tournament is 80% and the probability that team B will not win the tournament is 60%. If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?

(A) 20%
(B) 40%
(C) 48%
(D) 60%
(E) 80%
ShowHide Answer
Official Answer
D
Most Helpful Reply
User avatar
BrentGMATPrepNow
User avatar
Major Poster
Joined: 12 Sep 2015
Last visit: 31 Oct 2025
Posts: 6,733
Own Kudos:
36,459
 [3]
Given Kudos: 799
Location: Canada
Expert
Expert reply
Posts: 6,733
Kudos: 36,459
 [3]
The probability that team A will not win the tournament is 80% and the 26 Mar 2018, 10:09
1
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
Bunuel
The probability that team A will not win the tournament is 80% and the probability that team B will not win the tournament is 60%. If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?

(A) 20%
(B) 40%
(C) 48%
(D) 60%
(E) 80%
Show more

The probability that team A will NOT win the tournament is 80%
In other words, the probability that team A will NOT win the tournament is 0.8
So P(team A WILL win the tournament) = 1 - 0.8 = 0.2

The probability that team B will NOT win the tournament is 60%
So P(team B WILL win the tournament) = 1 - 0.6 = 0.4

If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?
This is an OR probability. So, we'll apply the OR probability formula:

P(event X occurs OR event Y occurs ) = P(X occurs ) + P(Y occurs ) - P(X and Y BOTH occur)

So, we get: P(A or B wins tournament) = P(A wins tournament) + P(B wins tournament) - P(A AND B both win tournament)
= 0.2 + 0.4 - 0
= 0.6

Answer: D

ASIDE: P(A AND B both win tournament) = 0, because we are told that "there is only one tournament winner." So, both teams cannot win.

Cheers,
Brent
General Discussion
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 25 Apr 2026
Posts: 109,822
Own Kudos:
811,130
 [3]
Given Kudos: 105,878
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,822
Kudos: 811,130
 [3]
The probability that team A will not win the tournament is 80% and the 20 Mar 2018, 23:29
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
Bunuel
The probability that team A will not win the tournament is 80% and the probability that team B will not win the tournament is 60%. If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?

(A) 20%
(B) 40%
(C) 48%
(D) 60%
(E) 80%
Show more

21. Combinatorics/Counting Methods



For more:
ALL YOU NEED FOR QUANT ! ! !
Ultimate GMAT Quantitative Megathread
User avatar
Gladiator59
User avatar
Joined: 16 Sep 2016
Last visit: 18 Mar 2026
Posts: 840
Own Kudos:
2,716
 [2]
Given Kudos: 271
Status:It always seems impossible until it's done.
GMAT 1: 740 Q50 V40
GMAT 2: 770 Q51 V42
Products:
My Reviews
GMAT 2: 770 Q51 V42
Posts: 840
Kudos: 2,716
 [2]
The probability that team A will not win the tournament is 80% and the 21 Mar 2018, 00:20
2
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
The probability that team A will not win the tournament is 80% and the probability that team B will not win the tournament is 60%. If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?

(A) 20%
(B) 40%
(C) 48%
(D) 60%
(E) 80%
Show more

IMO D.

Let P(A) be probability that Team A wins the tournament.
P(A) = 1 - 0.8 = 0.2
P(B) = 1 - 0.6 = 0.4

P(A or B) = P(A) + P(B) .... ( as only one of them can win the tournament which means there is no overlap in the two events)
P(A or B) = 0.2 + 0.4
= 0.6 or 60%

Hence D.

Best,
Gladi
User avatar
rocko911
User avatar
Joined: 11 Feb 2017
Last visit: 12 Apr 2018
Posts: 157
Own Kudos:
37
Given Kudos: 206
Posts: 157
Kudos: 37
The probability that team A will not win the tournament is 80% and the 22 Mar 2018, 15:00
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Gladiator59
Bunuel
The probability that team A will not win the tournament is 80% and the probability that team B will not win the tournament is 60%. If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?

(A) 20%
(B) 40%
(C) 48%
(D) 60%
(E) 80%

IMO D.

Let P(A) be probability that Team A wins the tournament.
P(A) = 1 - 0.8 = 0.2
P(B) = 1 - 0.6 = 0.4

P(A or B) = P(A) + P(B) .... ( as only one of them can win the tournament which means there is no overlap in the two events)
P(A or B) = 0.2 + 0.4
= 0.6 or 60%

Hence D.

Best,
Gladi
Show more


How is it different from my way?

Prob. of A win and B not win = 20/100 * 60 /100

Prob. of B win and A not win = 40/100 * 80 /100

Any one can win so we need (+)

20/100 * 60 /100 + 40/100 * 80 /100


The result is not 60%


why?
User avatar
aserghe1
User avatar
Joined: 30 Mar 2017
Last visit: 26 Oct 2021
Posts: 83
Own Kudos:
174
 [1]
Given Kudos: 53
GMAT 1: 200 Q1 V1
Products:
My Reviews
GMAT 1: 200 Q1 V1
Posts: 83
Kudos: 174
 [1]
The probability that team A will not win the tournament is 80% and the 23 Mar 2018, 13:52
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
rocko911
Gladiator59
Bunuel
The probability that team A will not win the tournament is 80% and the probability that team B will not win the tournament is 60%. If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?

(A) 20%
(B) 40%
(C) 48%
(D) 60%
(E) 80%

IMO D.

Let P(A) be probability that Team A wins the tournament.
P(A) = 1 - 0.8 = 0.2
P(B) = 1 - 0.6 = 0.4

P(A or B) = P(A) + P(B) .... ( as only one of them can win the tournament which means there is no overlap in the two events)
P(A or B) = 0.2 + 0.4
= 0.6 or 60%

Hence D.

Best,
Gladi


How is it different from my way?

Prob. of A win and B not win = 20/100 * 60 /100

Prob. of B win and A not win = 40/100 * 80 /100

Any one can win so we need (+)

20/100 * 60 /100 + 40/100 * 80 /100


The result is not 60%


why?
Show more

I dont understand the statement "Prob. of A win and B not win" because if A wins, then by default B does not win since there can only be 1 winner. Team A winning implies that every other team does not win, so (Prob. of A win and B not win) = (Prob. of A win) = 20%.
User avatar
Gladiator59
User avatar
Joined: 16 Sep 2016
Last visit: 18 Mar 2026
Posts: 840
Own Kudos:
2,716
 [1]
Given Kudos: 271
Status:It always seems impossible until it's done.
GMAT 1: 740 Q50 V40
GMAT 2: 770 Q51 V42
Products:
My Reviews
GMAT 2: 770 Q51 V42
Posts: 840
Kudos: 2,716
 [1]
The probability that team A will not win the tournament is 80% and the 23 Mar 2018, 14:09
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
aserghe1
rocko911
Gladiator59


IMO D.

Let P(A) be probability that Team A wins the tournament.
P(A) = 1 - 0.8 = 0.2
P(B) = 1 - 0.6 = 0.4

P(A or B) = P(A) + P(B) .... ( as only one of them can win the tournament which means there is no overlap in the two events)
P(A or B) = 0.2 + 0.4
= 0.6 or 60%

Hence D.

Best,
Gladi


How is it different from my way?

Prob. of A win and B not win = 20/100 * 60 /100

Prob. of B win and A not win = 40/100 * 80 /100

Any one can win so we need (+)

20/100 * 60 /100 + 40/100 * 80 /100


The result is not 60%


why?

I dont understand the statement "Prob. of A win and B not win" because if A wins, then by default B does not win since there can only be 1 winner. Team A winning implies that every other team does not win, so (Prob. of A win and B not win) = (Prob. of A win) = 20%.
Show more

Hi rocko911,

precisely.. this is why the final answer is incorrect as rightly pointed out by aserghe1.


When we are applying the probability of A winning.. B losing is implicit - as these are mutually exclusive events. ( or in other words .. there can only be one winner)

Does that make sense?

Best,
Gladi
User avatar
EgmatQuantExpert
User avatar
e-GMAT Representative
Joined: 04 Jan 2015
Last visit: 02 Apr 2024
Posts: 3,657
Own Kudos:
20,880
Given Kudos: 165
Expert
Expert reply
Posts: 3,657
Kudos: 20,880
The probability that team A will not win the tournament is 80% and the 26 Mar 2018, 09:42
Kudos
Add Kudos
Bookmarks
Bookmark this Post

Solution:



Given:

    • P (Team A not winning the tournament) = 80% = 80/100

    • P (Team B not winning the tournament) = 60% = 60/100

    • The tournament has only 1 winner.


Working out:

We need to find that either team A or team B wins the tournament.

Per our conceptual knowledge, we know the following:

    • P (Non-event) = 1 – P(Event)

P (Team A winning the tournament) = 1 – 80/100 = 20/100

P (Team B winning the tournament) = 1- 60/100 = 40/100

Since it is already stated in the question stem that the tournament has only a single winner, the above two events must be independent.

Hence, P (Either Team A wins or Team B wins) = 20 /100 + 40/100 = 60/100, or, 60%.

Answer: Option D
User avatar
ScottTargetTestPrep
User avatar
Target Test Prep Representative
Joined: 14 Oct 2015
Last visit: 24 Apr 2026
Posts: 22,286
Own Kudos:
26,534
Given Kudos: 302
Status:Founder & CEO
Affiliations: Target Test Prep
Location: United States (CA)
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 22,286
Kudos: 26,534
The probability that team A will not win the tournament is 80% and the 27 Mar 2018, 11:32
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
The probability that team A will not win the tournament is 80% and the probability that team B will not win the tournament is 60%. If there is only one tournament winner, what is the probability that either team A or team B wins the tournament?

(A) 20%
(B) 40%
(C) 48%
(D) 60%
(E) 80%
Show more

Recall that P(A or B) = P(A) + P(B) - P(A and B). The probability that team A wins is 1 - 0.8 = 0.2 and the probability that team B wins is 1 - 0.6 = 0.4. Since they can’t both be the winner, P(A and B) = 0. Thus,

P(A or B) = 0.2 + 0.4 - 0 = 0.6

Answer: D
User avatar
GmatPoint
User avatar
Joined: 02 Jan 2022
Last visit: 13 Oct 2022
Posts: 246
Own Kudos:
140
Given Kudos: 3
GMAT 1: 760 Q50 V42
GMAT 1: 760 Q50 V42
Posts: 246
Kudos: 140
The probability that team A will not win the tournament is 80% and the 20 Jun 2022, 05:13
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Probability of A winning the tournament = 1 - 0.8 = 0.2
Similarly, Probability of B winning the tournament = 0.4

Thus,probability that either team A or team B wins the tournament = 0.2 + 0.4 = 0.6
Or, the probability that either team A or team B wins the tournament = 60%

Thus, the correct option is D.
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,977
Own Kudos:
1,117
Posts: 38,977
Kudos: 1,117
The probability that team A will not win the tournament is 80% and the 08 Nov 2025, 03:38
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Bunuel
Math Expert
109822 posts
Krunaal
Tuck School Moderator
853 posts