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Puzzle Plex

Today's Puzzle

Today was Catherine´s birthday. She turned 24. Catherine is twice as old as Ryan was when Catherine was as old as Ryan now. How old is Ryan now?..................


Set Theory

Practice Questions on Set Theory



Set Theory:


The set which does not contain any element is known as an empty set or a null set.
If every point of set A belongs to B then A is contained or included in B & called suset of B. B is called trhe superset of a.This is represented as A ⊂ B or B ⊃ A
Two sets are identical,if they contain exactly same points and is then denoted as A = B.Another way to represent this is A = B if and only if A ⊂ B or B ⊂ A


Operation with Sets:


The union of two sets A and B (A ∪ B) is the set of points which belongs to atlease one of them.
The intersection of two sets A and B (A ∩ B) is the set of points which belongs to both of them.
Sets obey commutative law od union and intersection.
A ∪ B = B ∪ A ; A ∩ B = B ∩ A
Sets obey associative law of union and intersection
(A ∪ B) ∪ C = A ∪ (B ∪ C)
(A ∩ B) ∩ C = A ∩ (B ∩ C)
Sets obey distributive law of union and intersection
(A ∪ B) ∩ C = (A ∩ C) ∪ (B ∩ C)
(A ∩ B) ∪ C = (A ∪ C) ∩ (B ∪ C)


De Morgan's Law:


(A ∪ B)c = Ac ∩ Bc
(A ∩ B)c = Ac ∪ Bc