Official answer:
Let a, b, and c be the numbers, respectively, of members in Groups P and M but not T, Groups P and T but not M, and Groups M and T but not P. The labeled diagram below shows for each of the 7 regions in the original diagram the number of stockholders in terms of a, b, and c. For example, since there are 12 members in Group M, it follows that the number of members in Group M only is 12 − (a + 8 + c) = 4 − a − c.
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We are to assume that each member of Group M belongs to Group P and determine the maximum possible number of members belonging to both Group T and Group P. From our assumption, it follows that 4 −
a −
c = 0 and
c = 0, or
a = 4 and
c = 0. Using this information, and suppressing information about Group M (which is not relevant to answer the question), the labeled diagram above can be replaced with the labeled diagram below:
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Because each of the three regions represents a nonnegative number of members, it follows that 237 −
b ≥ 0, or
b ≤ 237. Therefore, the number of members belonging to both Group T and Group P, namely 8 +
b, is no more than 8 + 237 = 245. Moreover, letting
a = 4,
b = 237, and
c = 0, it is easy to see from the first labeled diagram above that it is possible to have 245 members belonging to both Group T and Group P.
The correct answer is 245.We are to assume that the number of members belonging to Group M and Group P is 10 and determine the maximum possible number of members belonging to both Group T and Group M. From our assumption, it follows that
a + 8 = 10, or
a = 2. Using this information, the first labeled diagram above can be replaced with the labeled diagram below:
Because 2 −
c cannot be negative, it follows that
c ≤ 2. Therefore, the number of members belonging to both Group T and Group M, namely 8 +
c, is no more than 8 + 2 = 10. Moreover, letting
a = 2,
b = 0, and
c = 2, it is easy to see from the first labeled diagram above that it is possible to have 10 members belonging to both Group T and Group M.
The correct answer is 10.