Question

If $N_a=\{an:n\in N\}$ , then $N_3\cap N_4$ =

• A. $N_7$
• B. $N_{12}$
• C. $N_3$
• D. $N_4$

Answer 1

The correct option is B

$N_{12}$

$N_a=\{an:n\in N\}$
$N_3\cap N_4=\{3,6,9,12,15\dots \dots \}\cap \{4,8,12,16,20,\dots \dots \}$

$=\{12,24,36\dots \dots \}=N_{12}$

[$\because$ 3,4 are relatively prime numbers ]
$\therefore$ $N_3\cap N_4$ = $N_{12}$