Probability : IR Question : Integrated Reasoning (IR)
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Probability : IR Question

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16 May 2012, 04:47
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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
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http://www.mba.com/the-gmat/nex-gen/samples/sample-275.aspx

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Re: Probability : IR Question [#permalink]

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16 May 2012, 04:58
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
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Vaibhav

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

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Re: Probability : IR Question [#permalink]

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16 May 2012, 05:40
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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
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Re: Probability : IR Question [#permalink]

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16 May 2012, 11:25
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.
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Re: Probability : IR Question [#permalink]

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31 May 2012, 01:38
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
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Re: Probability : IR Question [#permalink]

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01 Jun 2012, 08:24
I think its ..1/3

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

plz share ans of this question.
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Re: Probability : IR Question [#permalink]

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05 Jun 2012, 15:23
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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
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Re: Probability : IR Question [#permalink]

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07 Jun 2012, 20:14
I can also get 5/6 and 1/3.
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Re: Probability : IR Question [#permalink]

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11 Jul 2012, 07:29
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
Re: Probability : IR Question   [#permalink] 11 Jul 2012, 07:29
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