Let R be a relation from the set 1,2,3 ldots ldots, 60 to itself such that R= (a, b): b=p q, where p, q ≥ 3 are prime numbers . Then, the number of elements in Ris:

Question

Let R be a relation from the set 1,2,3 ldots ldots, 60 to itself such that R= (a, b): b=p q, where p, q ≥ 3 are prime numbers . Then, the number of elements in Ris: (A) 600 (B) 660 (C) 540 (D) 720

Tardigrade Admin · Accepted Answer

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 q =5,7,11 If p =7 q =7 Total cases =60 × 11=660

Q. Let $R$ be a relation from the set ${1, 2, 3 \dots\dots, 60}$ to itself such that $R = {(a, b) : b = pq$ , where $p, q \geq 3$ are prime numbers $}$ . Then, the number of elements in Ris:

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 Ris:

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 ${1, 2, 3 \dots\dots, 60}$ to itself such that $R = {(a, b) : b = pq$ , where $p, q \geq 3$ are prime numbers $}$ . Then, the number of elements in Ris:

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 $= 60 \times 11 = 660$