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A marketing firm determined that, of 200 households [#permalink]
 28 Apr 2008, 18:14
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A marketing firm determined that, of 200 households surveyed, 80 used neither Brand A nor Brand B soap, 60 usd only Brand A soap, and for every household that used both brands of soap, 3 used only Brand B soap. How many of the 200 households surveyed used both brands of soap? A. 15 B. 20 C. 30 D. 40 E. 45
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Director
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Total Household = 200
Number of household who do not use any brands of soap = 80
Number of household who use any brands of soap = 200 - 80 = 120
Number of household who use brands A of soap = 60
Say x people used both brands, then 3*x = 3x people used only brand B.
As per Set theory
120 = 60 + 3x - x
=> 2x = 60
=> x = 30
Answer C.
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Director
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Sorry got wrong calculation. Questions said "every household that used both brands of soap, 3 used only Brand B soap."
So if Say x people used both brands, then 3*x = 3x people used only brand B.
Then total number of people using brand B = 3x + x = 4x
So As per Set theory
120 = 60 + 4x - x
=> x = 20
Answer B.
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Director
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See attached
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SVP
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abhijit_sen wrote: Answer B. Abhijit, thank for your support, but still be wrong!  jbpayne wrote: See attached thank jbpayne, but I am not a fan of diagram, it make me confused! I like the equation: Total = group A + group B - group (AB)... and I am trying to set it up!
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Director
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The equation also works, but you need to know how to use the diagram as well. Try using the equation when you have three different groups instead of just two. It won't work nearly as easily as a picture.
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Manager
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abhijit_sen wrote: Sorry got wrong calculation. Questions said "every household that used both brands of soap, 3 used only Brand B soap."
So if Say x people used both brands, then 3*x = 3x people used only brand B.
Then total number of people using brand B = 3x + x = 4x
So As per Set theory
120 = 60 + 4x - x
=> x = 20
Answer B. Hey Abhijit, Brother u are close but u made a silly mistake 3x people used only brand B. so it is 120=60(only A)+3x(Only B)+x(Both) Ans is 15
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Director
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Just a bad day. Getting couple of wrongs do not know why? May be over worked.
Formula still holds correctly. Rohit pointed out well. Cheers mate.
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