GATE CS 2016 Set 2 — Question 6
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Question
Among 150 faculty members in an institute, 55 are connected with each other through Facebook® and 85 are connected through WhatsApp®. 30 faculty members do not have Facebook® or WhatsApp® accounts. The number of faculty members connected only through Facebook® accounts is ______________.
Correct answer
(A) 35
Solution
Let be the set of faculty members connected through Facebook and be the set of faculty members connected through WhatsApp.
Total faculty members .
Number of members with neither account .
Therefore, the number of members with at least one account is:Given:Using the formula for the union of two sets:The number of faculty members connected ONLY through Facebook is:
Total faculty members .
Number of members with neither account .
Therefore, the number of members with at least one account is:Given:Using the formula for the union of two sets:The number of faculty members connected ONLY through Facebook is:
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