It is currently 17 Nov 2017, 11:10

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Probability : IR Question

Author Message
TAGS:

### Hide Tags

Intern
Joined: 11 Apr 2012
Posts: 14

Kudos [?]: 13 [1], given: 2

### Show Tags

16 May 2012, 05:47
1
KUDOS
5
This post was
BOOKMARKED
Hi ,

I found the attached question in GMAT IR Samples . I found the answers rather strange.

Can someone help me to understand how to solve this problem.

Thanks
Bharath
Attachments

http://www.mba.com/the-gmat/nex-gen/samples/sample-275.aspx

Capture.PNG [ 44.08 KiB | Viewed 8457 times ]

Kudos [?]: 13 [1], given: 2

Manager
Affiliations: Project Management Professional (PMP)
Joined: 30 Jun 2011
Posts: 197

Kudos [?]: 83 [0], given: 12

Location: New Delhi, India
Re: Probability : IR Question [#permalink]

### Show Tags

16 May 2012, 05:58
mazerath wrote:
Hi ,

I found the attached question in GMAT IR Samples . I found the answers rather strange.

Can someone help me to understand how to solve this problem.

Thanks
Bharath

Hi Mazerath

can you plz share the answers

Best
Vaibhav
_________________

Best
Vaibhav

If you found my contribution helpful, please click the +1 Kudos button on the left, Thanks

Kudos [?]: 83 [0], given: 12

VP
Joined: 24 Jul 2011
Posts: 1354

Kudos [?]: 650 [4], given: 20

GMAT 1: 780 Q51 V48
GRE 1: 1540 Q800 V740
Re: Probability : IR Question [#permalink]

### Show Tags

16 May 2012, 06:40
4
KUDOS
The key here is to combine the knowledge of sets with the information given in the figure.
E.g.:
Number of high school graduates = number of students outside the circle marked 'no high school diploma' = 300 - 90 = 210

(a) In the given figure, number of students under 30 = 140
Number of students who are high school graduates = 210
Number of students who are both under 30 and high school graduates = 100
=> Number of students who are under 30 or high school graduates = 140 + 210 - 100 = 250 (using the sets formula n(A U B) = n(A) + n(B) - n(A n B) )
Therefore probability = 250 / 300 = 5/6

(b) Prob that student is both under 30 and a high school graduate = 100/300 = 1/3
_________________

GyanOne | Top MBA Rankings and MBA Admissions Blog

Premium MBA Essay Review|Best MBA Interview Preparation|Exclusive GMAT coaching

Get a FREE Detailed MBA Profile Evaluation | Call us now +91 98998 31738

Kudos [?]: 650 [4], given: 20

Intern
Joined: 11 Apr 2012
Posts: 14

Kudos [?]: 13 [0], given: 2

Re: Probability : IR Question [#permalink]

### Show Tags

16 May 2012, 12:25
narangvaibhav wrote:
mazerath wrote:
Hi ,

I found the attached question in GMAT IR Samples . I found the answers rather strange.

Can someone help me to understand how to solve this problem.

Thanks
Bharath

Hi Mazerath

can you plz share the answers

Best
Vaibhav

please check the file 's comment section. I am not able to paste URLs as I am still a very new member.

Kudos [?]: 13 [0], given: 2

Manager
Joined: 12 May 2012
Posts: 80

Kudos [?]: 120 [0], given: 14

Location: India
Concentration: General Management, Operations
GMAT 1: 650 Q51 V25
GMAT 2: 730 Q50 V38
GPA: 4
WE: General Management (Transportation)
Re: Probability : IR Question [#permalink]

### Show Tags

31 May 2012, 02:38
mazerath wrote:
Hi ,

I found the attached question in GMAT IR Samples . I found the answers rather strange.

Can someone help me to understand how to solve this problem.

Thanks
Bharath

I believe they are 5/6 and 1/3

Kudos [?]: 120 [0], given: 14

Senior Manager
Joined: 06 Aug 2011
Posts: 388

Kudos [?]: 238 [0], given: 82

Re: Probability : IR Question [#permalink]

### Show Tags

01 Jun 2012, 09:24
I think its ..1/3

and ..10^10/30^10 ..I m not sure

plz share ans of this question.
_________________

Bole So Nehal.. Sat Siri Akal.. Waheguru ji help me to get 700+ score !

Kudos [?]: 238 [0], given: 82

Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 4488

Kudos [?]: 8730 [3], given: 105

Re: Probability : IR Question [#permalink]

### Show Tags

05 Jun 2012, 16:23
3
KUDOS
Expert's post
manulath wrote:

I believe they are 5/6 and 1/3

Hi, there. I'm happy to contribute here.

First of all, this question, and the OA, can be found at:
http://www.mba.com/the-gmat/nex-gen/sam ... x?next=yes

This is from one of the "old" sample IR questions that GMAC released, so presumably not as representative of the IR section as the online material that accompanies the OG13.

I can guarantee the OAs are as follows:
1) If one student is selected at random from the 300 surveyed, the chance that the student will be under 30 or a high school graduate or both is 5/6.

2) If one student is selected at random from the 300 surveyed, the chance that the student will be both under 30 and a high school graduate is 1/3.

There are 30 "ticks" in the diagram --- for the first, we are including everyone except the folks who are over 30 and have no high school diploma -- those would be the five ticks in the central overlap oval --- so the other 25 ticks are "legal" for the first question, and 25/30 = 5/6.

For the second question, we only want folks under thirty (outside of the right circle) and have a HS diploma (outside the left circle also) --- so the only "legal' ticks are the row of 10 ticks hovering above both circles --- 10/30 = 1/3.

Does all that make sense?

Here's a link to a free IR eBook I wrote:
http://magoosh.com/gmat/2012/gmat-integ ... ing-ebook/

I hope that helps. Let me know if anyone has any IR related questions.

Mike
_________________

Mike McGarry
Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

Kudos [?]: 8730 [3], given: 105

Intern
Joined: 29 May 2012
Posts: 15

Kudos [?]: [0], given: 0

GMAT 1: 680 Q51 V29
GPA: 3.94
Re: Probability : IR Question [#permalink]

### Show Tags

07 Jun 2012, 21:14
I can also get 5/6 and 1/3.

Kudos [?]: [0], given: 0

Intern
Joined: 01 Apr 2012
Posts: 25

Kudos [?]: [0], given: 11

Re: Probability : IR Question [#permalink]

### Show Tags

11 Jul 2012, 08:29
what about using a table such as this:

<30......>=30...total
_________________
4.........5........9......No. H
_________________
10......11......21......H
_________________
14......16......30......Total

No. H= No high school; H=High school
the total (30), the total no high school (9), the total 30 or above (16) and the intersection (5) could be directly taken from the diagram while others are computed. Thus, a) 4+10+5=25/30 b)10/30

Kudos [?]: [0], given: 11

Intern
Joined: 05 Jan 2017
Posts: 26

Kudos [?]: 3 [0], given: 18

Location: India
GMAT 1: 540 Q35 V29
Re: Probability : IR Question [#permalink]

### Show Tags

07 Mar 2017, 22:50
What I am reading wrong here? 11 ticks are for 30 years or older and 5 ticks for 30 years and older and no diploma. that's total 35 ticks for 30 years and older and 9 tickets for no dipolma. there are 10 ticks outside the both circles. those 10 ticks are 30 years and under and with high school diploma - so Number of students who are under 30 or high school graduates is 100/300 = 1/3 but OA is 5/6.

Where did i commit mistake in understanding the diagram?

Kudos [?]: 3 [0], given: 18

Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 4488

Kudos [?]: 8730 [0], given: 105

Re: Probability : IR Question [#permalink]

### Show Tags

08 Mar 2017, 15:12
kuvshah wrote:
What I am reading wrong here? 11 ticks are for 30 years or older and 5 ticks for 30 years and older and no diploma. that's total 35 ticks for 30 years and older and 9 tickets for no dipolma. there are 10 ticks outside the both circles. those 10 ticks are 30 years and under and with high school diploma - so Number of students who are under 30 or high school graduates is 100/300 = 1/3 but OA is 5/6.

Where did i commit mistake in understanding the diagram?

Dear kuvshah,

I'm happy to respond.

My friend, I think you are getting confused on "and" and "or." Those are absolutely crucial words in probability. You were basically correct for counting ticks in groups. There are 30 ticks total.
Group A = 30 or older AND has HS diploma (left lune) = 11 ticks
Group B = 30 or older AND has no HS diploma (overlap) = 5 ticks
Group C = under 30 AND has no HS diploma (right lune) = 9 ticks
Group D = under 30 AND has HS diploma (outside both circles) = 10 tickets

Question #1:
If one student is selected at random from the 300 surveyed, the chance that the student will be under 30 AND a high school graduate is ________ .
That's Group D only, over the whole, 10/30 = 1/3. That's the correct answer, but this was NOT the question asked in this problem.

Question #2:
If one student is selected at random from the 300 surveyed, the chance that the student will be under 30 OR a high school graduate OR both is ________.
This is the actual question asked in this IR problem, and the answer group is A & B & D, those three groups over the whole.
Group A people have the HS diploma, so they are in.
Group B people are under 30, to they are in.
Group D people are in on both counts.
All of these people are in (the only people not in are the 5 ticks in the overlap). Thus, 25 ticks over 30 ticks, 25/30 = 5/6.

You found the correct answer to the wrong question. Does this make sense?
Mike
_________________

Mike McGarry
Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

Kudos [?]: 8730 [0], given: 105

Intern
Joined: 11 Feb 2017
Posts: 23

Kudos [?]: 0 [0], given: 27

Location: India
Schools: SPJ PGPM"17
GMAT 1: 720 Q49 V38
GPA: 3.57
Re: Probability : IR Question [#permalink]

### Show Tags

27 Mar 2017, 02:39
a) student under 30 or high school grad or both

only 50 that is 5*10 does not satisfy this condition hence prob is 250/300 = 5/6

b) prob that student will be both under 30 and high school grad

only 100 i.e 10*10 satisfy this condition hence prob = 100/300 = 1/3

Kudos [?]: 0 [0], given: 27

Re: Probability : IR Question   [#permalink] 27 Mar 2017, 02:39
Display posts from previous: Sort by

# Probability : IR Question

Moderators: Bunuel, chetan2u

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.