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Let R be a relation from the set {1, 2, 3………,60} to itself such that R = {(a, b) : b = pq, where p, q ≥ 3 are prime numbers}. Then, the number of elements in R is : (A) 600 (B) 660 (C) 540 (D) 720 |
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Answer» Correct option is (B) 660 Number of possible values of a = 60, for b = pq, If p = 3, q = 3, 5, 7, 11, 13, 17, 19 If p = 5 q = 5, 7, 11 If p = 7 q = 7 Total cases = 60 x 11 = 660 |
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