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3 cards from this section. Quick, good the night before a test.
What is the cardinality of the union of sets A = {1, 2} and B = {2, 3}?
Consider what elements are shared.
How does adding the intersection help when calculating union?
Think about how many times each element appears.
What does the principle of inclusion-exclusion help prevent?
Think about how the overlap is handled.
In how many ways can the intersection of n sets be expressed?
Remember the pattern with positive and negative signs.
Given sets A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, and C = {5, 6, 7, 8}, calculate |A ∪ B ∪ C|.
Use inclusion-exclusion carefully for intersections.
If A1 to A5 have 3, 4, 5, 6, and 7 elements respectively, what is |A1 ∪ A2 ∪ A3 ∪ A4 ∪ A5| if some intersections are known?
Each intersection adjusts the counting!
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