Question

Given A = {2, 3, 4, 5}, B = {4, 5, 6, 7, 8} and the relation from A to B means, "is a factor of". Represent the relation by an arrow diagram.

Find the number of elements in the above relation.

Answer 1

$A=\{2,3,4,5\}$

$B=\{4,5,6,7,8\}$

$R$ is the set of all ordered pairs whose $1^{st}$ component is a factor of the $2^{nd}$ component.

$\therefore R=\left\{\right(2,4),(2,6),(2,8),(3,6),(5,5),(4,4),(4,8\left)\right\}$.

Thus the number of elements in the given set is $7$.