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#### OG - PS - #180

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 Post subject: OG - PS - #180  Posted: Tue Sep 11, 2007 3:08 pm
 What is the approach I should take to solve these? I initally wanted to substitute a number for (like 100) N but it didn't work In a nation wide poll, N people were interviewed. if 25% of them answered "yes" to Question 1, and of those, 33% answered Yes to Question 2. Which of the following expresssions would represent the number of people interviewed who did not answer "yes" to both? a N/7 b. 6N/7 c. 5N/12 d 7N/12 e 11N/12

 Post subject:   Posted: Wed Sep 12, 2007 2:33 pm
 ManhattanGMAT Staff

Posts: 6861
Location: San Francisco
 Plugging in a number will work here but you have to make sure it's a number that will work "nicely" in the problem. Also, the original problem does not give the numbers as 25% and 33% but as 1/4 and 1/3. This is important to note for two reasons: first, 33% is not the same number as 1/3 - close, but not the same. Second, the fact that the original problem is written in fractions gives you the clue as to what number to pick. You pick the common denominator - in this case, 4*3 = 12 - because then the numbers in the problem will work nicely. N = 12 1/4, or 3, answer Yes to Q1. Therefore 9 answer No to Q1 1/3 of the 3, or 1, answers Yes to Q2. Therefore, 2 of the 3 answer No to Q2. The number of people who answered Yes to both is 1. Therefore, the number of people who did NOT answer yes to both is 12-1 = 11. Test N=12 in the answers and find the one that equals 11. Only E works. _________________Stacey KoprinceInstructorDirector of Online CommunityManhattanGMAT

 Post subject: ok so..  Posted: Thu Sep 13, 2007 1:50 am
 it is using VIC and choosing a denominator that works for each fraction...thanks

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