Cars and students

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sat Dec 20, 2008 8:27 am

In a group of 80 college students, how many own a car?
(1) Of the students who own a car, 14 are male
(2) Of the students who do not own a car, 42% are female

Brent Hanneson - Creator of GMATPrepNow.com

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Source: Beat The GMAT — Data Sufficiency | Sat Dec 20, 2008 8:27 am

cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Sat Dec 20, 2008 9:13 am

I am getting E)

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720dreaming: Senior | Next Rank: 100 Posts; Posts: 45; Joined: Mon Dec 08, 2008 9:55 pm; Thanked: 4 times

by 720dreaming » Sat Dec 20, 2008 10:11 am

Getting C. x=own a car

from A

(x-14)=Female

From B

(80-x)(.42)=Female

2 equations, 2 unknowns.

Is there a flaw in my logic?

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logitech: Legendary Member; Posts: 2134; Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members; Thanked: 237 times; GMAT Score:730

by logitech » Sat Dec 20, 2008 10:21 am

720dreaming wrote:Getting C. x=own a car

from A

(x-14)=Female

From B

(80-x)(.42)=Female

2 equations, 2 unknowns.

Is there a flaw in my logic?

(x-14)=Female who have cars!
(80-x)(.42)=Female who does not have cars.

So not same kind of girls

LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"

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720dreaming: Senior | Next Rank: 100 Posts; Posts: 45; Joined: Mon Dec 08, 2008 9:55 pm; Thanked: 4 times

by 720dreaming » Sat Dec 20, 2008 10:28 am

I was expecting someone to correct my logic, something was missing in the question (based on my intuition), but formula SEEMED to work.

Thanks.

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720dreaming: Senior | Next Rank: 100 Posts; Posts: 45; Joined: Mon Dec 08, 2008 9:55 pm; Thanked: 4 times

by 720dreaming » Sat Dec 20, 2008 10:31 am

I was expecting someone to correct my logic, something was missing in the question (based on my intuition), but formula SEEMED to work.

Thanks.

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vishubn: Legendary Member; Posts: 574; Joined: Sun Jun 01, 2008 8:48 am; Location: Bangalore; Thanked: 28 times

by vishubn » Sat Dec 20, 2008 10:33 am

80 students----

A) of the students...14 male... no info on female.... INsuff

B) Same reasoning !! Insuff

C)Nothing

IMO E

vishu

KILL !! DIE !! or BEAT my FEAR !!! de@D END!!

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GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sat Dec 20, 2008 11:33 am

Hint: [spoiler]it's not E[/spoiler]
Another hint?

Brent Hanneson - Creator of GMATPrepNow.com

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logitech: Legendary Member; Posts: 2134; Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members; Thanked: 237 times; GMAT Score:730

Re: Cars and students

by logitech » Sat Dec 20, 2008 11:47 am

Brent Hanneson wrote:In a group of 80 college students, how many own a car?
(1) Of the students who own a car, 14 are male
(2) Of the students who do not own a car, 42% are female

St1) Insuf. We need to know females who own a car.
St2) 42% female, 58%male

42+58=100 but we have only 80 students.

if we keep the same ratio:

21 female / 29 male ( here is the magic in this question, 29 is a prime number so ) 21 female and 29 males do not have any car = 50 people

so 80-50 = 30 people have car - SUF

Choose B, great question.

LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Sat Dec 20, 2008 11:49 am

Brent,
If the question is complete as is then pl dont give any hints. This way we know what we missed.

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GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sat Dec 20, 2008 11:49 am

Exactly - we can't find 42% of many numbers and get a whole number (i.e., a whole person). Given the 42% part, this means that there must be 50 people without a car, and thus 30 people with a car.

Awesome! Great work, Logitech.
I think you're ready to take the GMAT

Brent Hanneson - Creator of GMATPrepNow.com

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