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If A = {1, 2,..., 60} and B is relation on A defined as B = {(x,y): y = pq where p and q are primes ≥ 3} then number of elements in B is:(a) 720(b) 660(c) 540(d) 600 |
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Answer» Correct option is (b) 660 Given y = pq {p,q are prime numbers ≥ 3} ∴y can be generated from 3x3,3x5,3x7,3×11,3x13,3×17,3x19,5x5,5x7,5x11,7x7 ⇒ Total 11 possibilties x can be {1,2,..., 60} Number of relations = 60 x 11 = 660 |
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