OG-11. QN: 180

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OG-11. QN: 180

by dinesh19aug » Wed Jul 14, 2010 5:11 pm
Q: In a nation wide poll, N people were interviewed on 2 questions. If 1/4 of them answered "Yes" to Question 1 and of those, 1/3 answered "Yes" to question 2, which of the following expressions represents the number of people who did not answer "Yes" to both questions

n/7

6n/7

5n/12

7n/12

11n/12

My approach

People who answered Q1 = n/4
People who answered Q2 = n/12
Total number of people who answered Yes = 1/4 + 1/12 = 1/3
People who did not answer yes to both the question = 1 -1/3 = 2n/3 .

Approach 2: I tried to solve it by double set amtrix as well, but that consused me more as I found that information was missing, because I did not knew how many people answered both the questions YES, How many people naswer Yes to 1 and No to 2 and how many answered Yes to 2 and no to 1.

Can Some one please explain.

The OA is E - 11N/12
Source: — Problem Solving |

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by this_time_i_will » Wed Jul 14, 2010 5:54 pm
People who did not reply yesy to both question = total number of people - number of people who replide yes to both
=N-(1/3)*(1/4)N
=11/12N

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by this_time_i_will » Wed Jul 14, 2010 5:57 pm
dinesh19aug wrote:People who answered Q2 = n/12
n/12 is number of people who Answered yes to both

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by Testluv » Thu Jul 15, 2010 1:23 am
The above poster is correct.

We know that n/4 answered "yes" to the first question, and that 1/3 of these, so n/12, also answered "yes" to the second question. So, any other person who answered "yes" to the second question would have answered "no" to the first.

Thus, n/12 is the fraction of people who answered "yes" to both questions.
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