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 :
← JEE Main 2022 · 29 Jul · Shift 1
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JEE Main 2022 · 29 Jul · Shift 1, Mathematics question 1
Answer and worked solution
Official answer: B
Possible b. Products of two odd primes up to 60: 9, 15, 21, 33, 39, 51, 57, 25, 35, 55, 49, which is 11 values.
Pairs. Any a works, so .
(B)
Topics:Relations