Q. If $N_{a} = {an : n \in N},$ then $N_{5} \cap N_{7}$ is equal to:

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A

$N_{7}$

B

$N$

C

$N_{35}$

D

$N_{5}$

E

$N_{12}$

Solution:

$∵$ $N_{5} = (5, 10, 15, 20, 25, 30, 35, ...)$
and $N_{7} = {7, 14, 21, 35, ...}$
$∴$ $N_{5} \cap N_{7} = {35, 70, .....} = N_{35}$