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 ≥ 3 are prime numbers . Then, the number of elements in R is :

Question

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 ≥ 3 are prime numbers . Then, the number of elements in R is : (A) 600 (B) 660 (C) 540 (D) 720

Tardigrade Admin · Accepted Answer

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 × 11=660

Q. Let $R$ be a relation from the set ${1, 2$ , $3. \dots\dots\dots, 60}$ 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 :

600

660

540

720

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 $= 60 \times 11 = 660$

Q. 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 :

600

660

540

720

Number of possible values of a=60, for b= pq, If p=3,q=3,5,7,11,13,17,19 If p=5q=5,7,11 If p=7q=7 Total cases =60×11=660

Q. Let $R$ be a relation from the set ${1, 2$ , $3. \dots\dots\dots, 60}$ 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 :

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 $= 60 \times 11 = 660$