![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
Select two different natural numbers and then determine whether
\the product is a natural number.
\ \Try some examples.
\![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=fa41c8746dff84eb526f5ca7eb149f1c.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=f0f8cf5791952f8762edaf74a5bbc0b9.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=a45cc3832b10ecaef257b55d0be9568d.png\")
Since the products of each pair of natural numbers are natural numbers, the set
\of natural numbers is closed under multiplication.![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
The set of natural numbers is closed under multiplication.