JEE Mains · Maths · STD 11 - 6. permutation and combination
Let \(R\) be a relation from the set \(\{1,2,3 \ldots \ldots \ldots, 60\}\) to itself such that \(R =\{( a , b ): b = pq\), where \(p , q \geq 3\) are prime numbers \(\}\). Then, the number of elements in \(R\) is.
- A \(600\)
- B \(660\)
- C \(540\)
- D \(720\)
Answer & Solution
Correct Answer
(B) \(660\)
Step-by-step Solution
Detailed explanation
Number of possible values of \(a=60\), for \(b=p q\), If \(p =3, q =3,5,7,11,13,17,19\) If \(p =5 \quad q =5,7,11\) If \(p =7 \quad q =7\) Total cases \(=60 \times 11=660\)
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