Author 
Message 
TAGS:

Hide Tags

SVP
Joined: 12 Sep 2015
Posts: 2316
Location: Canada

At a certain school, 40 percent of the students play rugby [#permalink]
Show Tags
20 Sep 2016, 13:49
Question Stats:
65% (01:46) correct 35% (01:19) wrong based on 148 sessions
HideShow timer Statistics
At a certain school, 40 percent of the students play both rugby and play chess. If 40 percent of the students who play rugby do not play chess, what percent of the students play rugby? A) 60 B) 66 2/3 C) 72 D) 75 E) 80 Kudos for all correct solutions
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Brent Hanneson – Founder of gmatprepnow.com



Board of Directors
Status: Stepping into my 10 years long dream
Joined: 18 Jul 2015
Posts: 3355

Re: At a certain school, 40 percent of the students play rugby [#permalink]
Show Tags
21 Sep 2016, 01:21
2
This post received KUDOS
2
This post was BOOKMARKED
GMATPrepNow wrote: At a certain school, 40 percent of the students play both rugby and play chess. If 40 percent of the students who play rugby do not play chess, what percent of the students play rugby? A) 60 B) 66 2/3 C) 72 D) 75 E) 80 Kudos for all correct solutions Let total be 100. A : Only Rugby B : Both Rugby and Chess C : Only Chess A+B+C =100 Also, B = 40 (Given) We are given 40% of (A+B) = A or 2 (A+40) = 3A or A = 80/3 Now, We need to find (A+B)/Total *100 = 66 2/3. Hence, B is the answer.
_________________
How I improved from V21 to V40! ? How to use this forum in THE BEST way? New > How ApplicantLab made me reach my 10 years long MBA dream?



Intern
Joined: 23 May 2016
Posts: 24
Location: United States (WA)
GPA: 3.5
WE: Engineering (Energy and Utilities)

Re: At a certain school, 40 percent of the students play rugby [#permalink]
Show Tags
21 Sep 2016, 12:28
2
This post received KUDOS
1
This post was BOOKMARKED
Explanation:
40% of Total Students play Rugby and Chess.
40% of Rugby players only play Rugby > 60% of rugby players play rugby and chess > 60%R = 40% Total Students
Rugby = 40%/60% x Total Students = 66 2/3% Total Students



Intern
Joined: 21 Sep 2016
Posts: 29

Re: At a certain school, 40 percent of the students play rugby [#permalink]
Show Tags
05 Sep 2017, 19:09
Solved this in another way, though I must confess I don't know whether that's correct or not, but let me present it:
Imo, this is a conditional probability problem. Let R be "people that play rugby" and C, "people that play chess".
We know that:
1) P(C and R) = 0,4 2) P(not C  R) = 0,4
Looking at 2), we know that P(not C  R) = 1  P(CR), thus: P(CR) = 0,6
Now, we know that P(CR) = P(C and R) / P(R):
0,6 = 0,4 / P(R) > P(R) = 0,4/0,6 = 2/3 (B)



Senior Manager
Joined: 07 Sep 2014
Posts: 440
Concentration: Finance, Marketing

Re: At a certain school, 40 percent of the students play rugby [#permalink]
Show Tags
29 Sep 2017, 20:43
abhimahna wrote: GMATPrepNow wrote: At a certain school, 40 percent of the students play both rugby and play chess. If 40 percent of the students who play rugby do not play chess, what percent of the students play rugby? A) 60 B) 66 2/3 C) 72 D) 75 E) 80 Kudos for all correct solutions Let total be 100. A : Only Rugby B : Both Rugby and Chess C : Only Chess A+B+C =100 Also, B = 40 (Given) We are given 40% of (A+B) = A or 2 (A+40) = 3A or A = 80/3 Now, We need to find (A+B)/Total *100 = 66 2/3. Hence, B is the answer. Aren't we forgetting people who are not going to play both chess and rugby. without mentioning the fact that all the student will play one of the game, this question can't be solved.




Re: At a certain school, 40 percent of the students play rugby
[#permalink]
29 Sep 2017, 20:43






