Question

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

Answer 1

Answer: (B)

660

Answer 2

b can take its values as 9, 15, 21, 33, 39, 51, 57, 25, 35, 55, 49
b can take these 11 values and a can take any of 60 values
Then, the number of elements in R = 60 × 11 = 660
So, the correct option is (B): 660