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Crazy problem solving question..

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by reach.ran » Sun Apr 27, 2008 9:28 am
Can someone please explain me how to derive this answer.. please.. thanks..Image
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Source: — Problem Solving |
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Location: so cal

by freedsl » Sun Apr 27, 2008 10:24 am
they are asking for bread only buyers which equals neiter( C or M) buyers which equals 1-probability of M&C ONLY buyers.


C only = 50-20 =30
M only = 40-20 =20



then P (M&C) = 20+30/100 or 1/2

1-1/2 =1/2 probability of M only.
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by reach.ran » Sun Apr 27, 2008 10:52 am
freedsl wrote:they are asking for bread only buyers which equals neiter( C or M) buyers which equals 1-probability of M&C ONLY buyers.


C only = 50-20 =30
M only = 40-20 =20



then P (M&C) = 20+30/100 or 1/2

1-1/2 =1/2 probability of M only.
Thanks for answereing, but the correct answer is 3/10 not 1/2. thanks again.. someone else please help me..
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by freedsl » Sun Apr 27, 2008 12:12 pm
What i did wrong was take 20 off twice, anyway

So you have the formula ALL buyers that trade in M and C (Unique buyers) = M+C- both (M&C) = 50+40-20 =70 the prob for this is 70/100 or 7/10

the opossite which would be only B buyers is 1- 7/10 =3/10
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Kaplan formula

by jscoligan » Mon Apr 28, 2008 3:24 pm
Cake+muffin+neither-both=Real total

50+40+neither-20=100

neither=30

30/100=> 3/10
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Re: Kaplan formula

by Stuart@KaplanGMAT » Mon Apr 28, 2008 7:43 pm
jscoligan wrote:Cake+muffin+neither-both=Real total

50+40+neither-20=100

neither=30

30/100=> 3/10
Kaching!

Perfect question for the overlapping sets formula:

True # of items = # with characteristic 1 + # with char 2 + # with neither char - # with both chars

In this case:

100 = 50 + 40 + neither - 20
100 = 70 + neither
30 = neither

So, probability of finding a "neither" person is 30/100 = 3/10
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