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m08 Q#7

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m08 Q#7 [#permalink] New post 01 Aug 2008, 09:56
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Among 200 people 56% like strawberry jam, 44% like apple jam, and 40% like raspberry jam. If 30% of people like both strawberry and apple jam, what is the largest possible number of people who like raspberry jam but do not like either strawberry or apple jam?

Answer:
The general equation is where denotes the number of people who like none of the three jams (draw the Veinn diagram). To maximize the number of people who like raspberry but not strawberry or apple jam has to be 0. The new equation can be rewritten as follows:
S + R + A - SA - AR - SR + SAR + N = 100%
........

I am not convinced with the formula given here:
Shouldn't the formula be:
S + R + A - SA - AR - SR - 2SAR + N = 100%


Thanks,
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Re: m08 Q#7 [#permalink] New post 02 Jun 2010, 10:22
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Among 200 people, 56% like strawberry jam, 44% like apple jam, and 40% like raspberry jam. If 30% of the people like both strawberry and apple jam, what is the largest possible number of people who like raspberry jam but do not like either strawberry or apple jam?

A. 20
B. 60
C. 80
D. 86
E. 92

The answer to this question is indeed B (60), but here is an interesting thing: everyone made mistakes either in formulas or in word translation (unfortunately the formula in OE is also incorrec).

First of all: "30% of the people like both strawberry and apple jam" doesn't mean that among these 30% can not be some people who like raspberry as well. Both strawberry and apple jam is the intersection of these two groups, if we refer to the diagram tejal777 posted it's the section x plus the section above it (the one 60 in it).

Next, no formula is needed to solve this question: 112 like strawberry jam, 88 like apple jam, 60 people like both strawberry and apple jam. So the # of people who like either strawberry or apple (or both) is 112+88-60=140 (on the diagram S+A). So there are TOTAL of 200-140=60 people left who "do not like either strawberry or apple jam". Can ALL these 60 people like raspberry? As R=80\geq{60}, then why not! So maximum # of people who like raspberry and don't like either strawberry or apple jam is 60.

Side note: min # of people who like raspberry and don't like either strawberry or apple jam would be zero (circle R is "inside" of two circles S and A). In this case these 60 people (who "do not like either strawberry or apple jam") will be those who like none of the 3 jams.

Answer: B.

There is a confusion about the formulas of 3 overlapping sets, hope my post at: formulae-for-3-overlapping-sets-69014.html#p729340 would help to clear this issue.
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Re: m08 Q#7 [#permalink] New post 03 Jun 2010, 03:37
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ykaiim wrote:
My answer is 80. As per Tejal's venn diagram, if there are no one like Rasberry+Apple, Strawberry+Rasberry and Strawberry+Rasberry+apple, then the number for Rasberry will be greatest = 80.

Please tell me where I am missing.

tejal777 wrote:
I have drawn a venn diagram.Please see where my error lies:
We need to find the shaded area= 80-x-y-z =??

Applying formula:
200=112+88-60+80-y-z+x
80-y-z+x=60
Hmm..Should'nt that be "-x"... Shocked


This approach is wrong because if you assume all sections mentioned by you (x, y and z in tejal777's diagram) to be zero than the sum would be more than 200: 140 who like either Strawberry or Apple (or both) plus 80 who like ONLY Raspberry (as you proposed) = 220>total.

By the way tejal777's diagram is wrong as he assumed that 60 is the # of people who like ONLY strawberry and apple.

Again please read for more on 3 overlapping sets at: formulae-for-3-overlapping-sets-69014.html#p729340

Hope it helps.
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Re: m08 Q#7 [#permalink] New post 14 Oct 2009, 13:40
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tejal777 wrote:
Wee bit confused here:
Should'nt the number of people who like raspberry jam but do not like either strawberry or apple jam be:
R-S-A-SAR instead of R-S-A+SAR??


It should be R+S+A-RS-RA-SA-2RSA+N=100%

R-RS-RA-2RSA=100%-N-S-A+SA

R-RS-RA-2RSA=100%-0-56%-44%+30% N is 0 because we want to maximize R

R-RS-RA-2RSA=30%

R-RS-RA-2RSA= people who only like R

30%*200people= 60 people
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Re: m08 Q#7 [#permalink] New post 08 Sep 2008, 17:16
i'm with you. anyone else think the formula was different?
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Re: m08 Q#7 [#permalink] New post 09 Sep 2008, 16:09
agreed.

But in all honesty, i drew a Venn to solve this one :)
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Re: m08 Q#7 [#permalink] New post 10 Sep 2008, 02:17
Sorry, guys. This is our mistake. We'll edit the typo.

Thanks everybody!
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Re: m08 Q#7 [#permalink] New post 05 Oct 2009, 04:06
Wee bit confused here:
Should'nt the number of people who like raspberry jam but do not like either strawberry or apple jam be:
R-S-A-SAR instead of R-S-A+SAR??
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Re: m08 Q#7 [#permalink] New post 06 Oct 2009, 22:24
I have drawn a venn diagram.Please see where my error lies:
We need to find the shaded area= 80-x-y-z =??

Applying formula:
200=112+88-60+80-y-z+x
80-y-z+x=60
Hmm..Should'nt that be "-x"... Shocked
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Re: m08 Q#7 [#permalink] New post 15 Oct 2009, 00:24
My bad :oops:. Promised to edit the typo and didn't do it. It's corrected now. The answer stays the same though.
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Re: m08 Q#7 [#permalink] New post 15 Oct 2009, 03:03
OMG..hold on a bit..formula time!

For 3 groups, the generic formula is:

True # of items = (total # in group 1) + (total # in group 2) + (total # in group 3) - (# in only 1/2) - (# in only 1/3) - (# in only 2/3) +(# in 1/2/3)

I have always always used this formula!!
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Re: m08 Q#7 [#permalink] New post 06 Dec 2009, 09:41
Can you please elaborate how did u solve this through Venn diagram?
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Re: m08 Q#7 [#permalink] New post 20 Mar 2010, 17:12
S + R + A - SA - AR - SR + SAR + N = 100%

S= 112
A =88
R =80

Lets say - SR - y , AR - z , SAR = x , N has to be 0 to maximize R
we want to find only R

112 + 88 + 80 -60 -y -z + x =200

solving
20-y-z+x =0
-(y+z-x) = -20
y+z -x = 20

Only R = R -(y+z -x) => 80-20 => 60 -Answer ( look at Tejal's post for venn diagram)_

I don't understand the other formula
R+S+A-RS-RA-SA-2RSA+N=100% - can some one explain how this formula is derived
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Re: m08 Q#7 [#permalink] New post 22 Mar 2010, 07:30
ichha148 wrote:
I don't understand the other formula
R+S+A-RS-RA-SA-2RSA+N=100% - can some one explain how this formula is derived


I think N is the number of people who dont like any JAM. Though, are we considering each person at least like one jam?
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Re: m08 Q#7 [#permalink] New post 02 Jun 2010, 04:30
My answer is 80. As per Tejal's venn diagram, if there are no one like Rasberry+Apple, Strawberry+Rasberry and Strawberry+Rasberry+apple, then the number for Rasberry will be greatest = 80.

Please tell me where I am missing.

tejal777 wrote:
I have drawn a venn diagram.Please see where my error lies:
We need to find the shaded area= 80-x-y-z =??

Applying formula:
200=112+88-60+80-y-z+x
80-y-z+x=60
Hmm..Should'nt that be "-x"... Shocked

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Re: m08 Q#7 [#permalink] New post 03 Jun 2010, 03:20
Bunuel,

This is great explaination. Thanks.
Can you please tell me where above in my explaination, I am missing?
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Re: m08 Q#7 [#permalink] New post 04 Jun 2011, 09:00
i solved by common sense.

60 is the number of guys who like both S and A

only straw = 112-60 = 52
only apple = 88-60 = 28


so number of people who do not like either strawberry or apple jam = 200-(60 +52+48)

pick B :roll:
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Re: m08 Q#7   [#permalink] 04 Jun 2011, 09:00
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