In a survey of town residents regarding three newspapers—*The Herald* (), *The Express* (), and *The Nation* ()—it was found that read *The Herald*, read *The Express*, and read *The Nation*. Furthermore, read both *The Herald* and *The Express*, read both *The Express* and *The Nation*, and read both *The Herald* and *The Nation*. If the number of residents who read none of these three newspapers is twice the number of those who read all three newspapers, how many residents read exactly two of the newspapers?
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- Answer
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Answer
The number of residents who read exactly two newspapers is .
Using the principle of inclusion-exclusion, , where is the number of residents reading all three newspapers. Since the number of residents reading none is , the total universe equation is , giving and . The number of residents reading exactly two newspapers is .
Step-by-Step Solution
Key Concept
Three-set inclusion-exclusion principle and Venn diagram cardinal region decomposition
Estimated Time:1m 30s