Question

* True or False? Natural Numbers are closed under division.

Answer 1

Answer: False

Natural numbers are not closed under division

Some natural numbers divide to get another natural number. For example, divide 10 over 2 to get 10/2 = 5.

However, there are infinitely many natural numbers that divide to get something that isn't a natural number. Example: 10/7 = 1.43 approximately. All we need is one counterexample to contradict the original statement.

A set is considered closed under division if dividing any two values in that set leads to another value in the set. More formally, if a & b are in some set then a/b must also be in the same set for that set to be closed under division.

If we changed "natural numbers" to "rational numbers", then that set is closed under division. If p, q are rational numbers then p/q is also rational. Basically, dividing any two fraction leads to some other fraction. The value of q cannot be zero.