Problem:
There are several sets of three different numbers whose sum is which can be chosen from . How many of these sets contain a
Answer Choices:
A.
B.
C.
D.
E.
Solution:
After the is selected, a sum of is needed. There are four pairs that yield . Thus there are four -element subsets which include and whose sum is .
Note. In the classic "magic square" there are lines through the middle of the square. The sum of the numbers along each line equals and includes the number .
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Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions