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Let A and B be two sets with |A| = 4 and |B| = 2. Find the number of subsets of A x B that each contain at least three elements.
- 275
- 510
- 219
- 256
Correct answer: 219
Solution
A x B has 4*2 = 8 elements. Subsets with at least 3 elements = 2⁸ - C(8,0) - C(8,1) - C(8,2) = 256 - 1 - 8 - 28 = 219.
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