Sample 275 mba.com

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anuprajan5: Master | Next Rank: 500 Posts; Posts: 279; Joined: Mon Jun 25, 2012 10:56 pmFollowed by: 10 members; Thanked: 60 times

by anuprajan5 » Wed Sep 12, 2012 12:41 pm

I was wondering if someone could help with this question.

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Source: Beat The GMAT — Data Insights | Wed Sep 12, 2012 12:41 pm

Jim@StratusPrep: MBA Admissions Consultant; Posts: 2279; Joined: Fri Nov 11, 2011 7:51 amFollowed by: 266 members; Location: New York; Thanked: 660 times; GMAT Score:770

by Jim@StratusPrep » Wed Sep 12, 2012 1:42 pm

Just count the number of symbols inside the circles -> 20

20/30 = 2/3

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anuprajan5: Master | Next Rank: 500 Posts; Posts: 279; Joined: Mon Jun 25, 2012 10:56 pmFollowed by: 10 members; Thanked: 60 times

by anuprajan5 » Wed Sep 12, 2012 9:20 pm

Jim,

Theres 2 issues with that - The number inside the circles would be people abobve 30 or that do not have a high school diploma or both, not under 30 or a high school graduate or both.

And your answer is 2/3 but the answer on the website is different - 5/6. (link below)

Regards
Anup

https://www.mba.com/the-gmat/nex-gen/sam ... x?next=yes

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ptkm: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Thu Sep 20, 2012 1:29 am

by ptkm » Sat Sep 22, 2012 4:07 am

From the pictograph, there are 40 students who are both >30 yr old and do not have diploma.
So total number of students who are either <30 yr old, or graduate high school, or both is 260.

The probability is 260/300 or 5/6.

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ptkm: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Thu Sep 20, 2012 1:29 am

by ptkm » Sat Sep 22, 2012 4:14 am

The second part, from the pictograph:
- 160 students are > 30 yr old so 140 students are < 30 year old.
- 80 students do not have diploma so 220 have diploma.

If there is no student who is both <30 yr old and has diploma, total number of students who are either <30 yr old or have diploma, or both is 140+220 = 360.

But we know this number is 260, that's because there are 360-260=100 students who satisfy both conditions.

So finally the probability is 100/300 = 1/3.

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anuprajan5: Master | Next Rank: 500 Posts; Posts: 279; Joined: Mon Jun 25, 2012 10:56 pmFollowed by: 10 members; Thanked: 60 times

by anuprajan5 » Sat Sep 22, 2012 8:25 am

PKm,

For the 2nd part of your answer, there is an essential error - the people who have no high school diploma is 90.

REgards
Anup

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Whitney Garner: GMAT Instructor; Posts: 273; Joined: Tue Sep 21, 2010 5:37 amFollowed by: 74 members; Location: Durham, NC; Thanked: 154 times; GMAT Score:770

Sample 275 mba.com

by Whitney Garner » Mon Oct 08, 2012 7:46 pm

anuprajan5 wrote:I was wondering if someone could help with this question.

Hi anuprajan5!

They have drawn this problem to be confusing!! I actually re-drew this problem to be an overlapping sets matrix, but I can show you that in a sec! We'll start with the algebra:

"What is the probability of selecting a student UNDER 30, or HS GRAD, or BOTH.
Let's find the areas that fit these and count the tick marks:
UNDER 30 = NOT in the circle on the left, so the 10 across the top and the 4 in the NO HS only circle.
HS GRAD = NOT in the circle on the right, so the 10 across the top (already counted those though), and the 11 in the left circle only.
BOTH = UNDER 30 + HS GRAD = neither in the circle on the left OR on the right, so those are the 10 across the top, but we already counted those.

Add them up: 10 + 4 + (skip the 10) + 11 + (skip the 10) = 10+4+11 = 25

Each counts for 10, so 250/300 = 25/30 = 5/6 or 5 out of 6!

ALTERNATE METHOD:
Let's build a double set matrix. We use the things that can overlap to label the top left box, and then we use the logical opposites of those for the titles next to them. Since NO HS and 30+ are the overlapping traits, the I'll put NO HS on the top left going across, and 30+ at the top left going down. Then HS would go next to NO HS (then total), and <30 below 30+ (then total).

Now we just fill in:
Overlap = 5 ticks = 50 ppl.
Total NO HS = 9 ticks = 90 ppl
Total 30+ = 16 ticks = 160ppl
Neither = 10 ticks = 100ppl
TOTAL = 300ppl

And now the 1-1.5 minute set-up make the questions a cinch!!

(1) <30, HS Grad, or Both

Add these blocks up: 110+40+100 = 250/300 = 25/30 = 5/6

(2) <30 AND a HS Grad

100/300 = 1/3.

Hope this helps!

Whit

Whitney Garner
GMAT/GRE/EA Instructor & Anxiety/Accommodations Coach
www.whitneygarner.com

Contributor to Beat The GMAT!

Math is a lot like love - a simple idea that can easily get complicated

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anuprajan5: Master | Next Rank: 500 Posts; Posts: 279; Joined: Mon Jun 25, 2012 10:56 pmFollowed by: 10 members; Thanked: 60 times

by anuprajan5 » Mon Oct 08, 2012 10:37 pm

Whitney,

You are my princess in white! I should have realized that a venn diagram with 2 paramaters could be drawn into a double matrix.

27 days before I get something that works

Regards
Anup

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