GMAT CLUB Official Explanation:A poll conducted among the members of a football fan club, revealed that 100 of them root for Portugal, 150 of them root for France, and 200 of them root for Argentina. Also, 150 of them root for exactly two of the three teams. How many members does the fan club have ?Check the diagram below:

Given:
(i) 100 people root for Portugal: \(a + d + f + g = 100\);
(ii) 200 people root for Argentina: \(b + e + d + g = 200\).
(iii) 150 people root for France: \(c + e + f + g = 150\);
(iiii) 120 people root for exactly two of the three teams: \(d + e + f = 150\).
The question asks to find \(total = a + b + c + d + e + f + g + N = ?\)Sum (i), (ii), and (iii):
\((a + d + f + g) + (b + e + d + g) + (c + e + f + g) = 450\);
\(a + b + c + 2(d + f+ e) + 3g = 450\).
Since given that \(d + e + f = 150\) (iiii), then:
\(a + b + c + 2*150+ 3g = 450.\);
\(a + b + c = 150 - 3g\)
Thus:
\(total = (a + b + c) + (d + e + f) + g + N = (150 - 3g) + 150 + g + N = 300 -2g + N=?\)
(1) Equal number of members root for Portugal only and for Argentina only.
This means that a = b, which is not sufficient to get the value of total = 300 -2g + N.
(2) For every 2 members of the club who root for none of the three teams, there is 1 member who roots for all three of the teams.
This means that \(N = 2g\). Thus, \(total = 300 - 2g + N = 300 -2g + 2g = 300\). Sufficient.
Answer: B.
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